diff --git a/Algorithms/FFT.cpp b/Algorithms/FFT.cpp
new file mode 100644
index 0000000..1f5fe39
--- /dev/null
+++ b/Algorithms/FFT.cpp
@@ -0,0 +1,91 @@
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+const int N = 500005;
+const double pi = acos(-1);
+struct complex
+{
+    double r, i;
+} a[N], b[N];
+inline complex operator+(const complex &x, const complex &y)
+{
+    return { x.r + y.r, x.i + y.i };
+}
+inline complex operator-(const complex &x, const complex &y)
+{
+    return { x.r - y.r, x.i - y.i };
+}
+inline complex operator*(const complex &x, const complex &y)
+{
+    return { x.r * y.r - x.i * y.i, x.r * y.i + x.i * y.r };
+}
+char s1[N], s2[N];
+int ans[N];
+void Rader(complex *F, int len)
+{
+    complex t;
+    int j = len >> 1;
+    for (int i = 1; i < len - 1; i++)
+    {
+        if (i < j)
+            t = F[i], F[i] = F[j], F[j] = t;
+        int k = len >> 1;
+        while (j >= k)
+            j -= k, k >>= 1;
+        if (j < k)
+            j += k;
+    }
+}
+void fft(complex *F, int len, int flag)
+{
+    Rader(F, len);
+    for (int h = 2; h <= len; h <<= 1)
+    {
+        const complex wn = { cos(-flag * 2 * pi / h), sin(-flag * 2 * pi / h) };
+        for (int j = 0; j < len; j += h)
+        {
+            complex w = { 1, 0 };
+            int m = h >> 1;
+            for (int k = j; k < j + m; k++, w = w * wn)
+            {
+                complex u = F[k], t = w * F[k + m];
+                F[k] = u + t, F[k + m] = u - t;
+            }
+        }
+    }
+}
+int main()
+{
+    while (~scanf("%s%s", s1, s2))
+    {
+        int len1, len2, len;
+        memset(a, 0, sizeof(a));
+        memset(b, 0, sizeof(b));
+        memset(ans, 0, sizeof(ans));
+        len1 = (int)strlen(s1) << 1, len2 = (int)strlen(s2) << 1;
+        for (len = 1; len < len1 || len < len2;)
+            len <<= 1;
+        len1 >>= 1, len2 >>= 1;
+        for (int i = 0; i < len1; i++)
+            a[i].r = s1[len1 - 1 - i] - '0';
+        for (int i = 0; i < len2; i++)
+            b[i].r = s2[len2 - 1 - i] - '0';
+        fft(a, len, 1);
+        fft(b, len, 1);
+        for (int i = 0; i < len; i++)
+            a[i] = a[i] * b[i];
+        fft(a, len, -1);
+        for (int i = 0; i < len; i++)
+            ans[i] = int(a[i].r / len + 0.5);
+        for (int i = 0; i < len; i++)
+            ans[i + 1] += ans[i] / 10, ans[i] %= 10;
+        int high = 0;
+        for (int i = len - 1; high == 0 && i >= 0; i--)
+            if (ans[i])
+                high = i;
+        for (int i = high; i >= 0; i--)
+            putchar(ans[i] + '0');
+        putchar('\n');
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/OnlineJudges/hdu/1402.cpp b/OnlineJudges/hdu/1402.cpp
new file mode 100644
index 0000000..1f5fe39
--- /dev/null
+++ b/OnlineJudges/hdu/1402.cpp
@@ -0,0 +1,91 @@
+#include <cmath>
+#include <cstdio>
+#include <cstring>
+const int N = 500005;
+const double pi = acos(-1);
+struct complex
+{
+    double r, i;
+} a[N], b[N];
+inline complex operator+(const complex &x, const complex &y)
+{
+    return { x.r + y.r, x.i + y.i };
+}
+inline complex operator-(const complex &x, const complex &y)
+{
+    return { x.r - y.r, x.i - y.i };
+}
+inline complex operator*(const complex &x, const complex &y)
+{
+    return { x.r * y.r - x.i * y.i, x.r * y.i + x.i * y.r };
+}
+char s1[N], s2[N];
+int ans[N];
+void Rader(complex *F, int len)
+{
+    complex t;
+    int j = len >> 1;
+    for (int i = 1; i < len - 1; i++)
+    {
+        if (i < j)
+            t = F[i], F[i] = F[j], F[j] = t;
+        int k = len >> 1;
+        while (j >= k)
+            j -= k, k >>= 1;
+        if (j < k)
+            j += k;
+    }
+}
+void fft(complex *F, int len, int flag)
+{
+    Rader(F, len);
+    for (int h = 2; h <= len; h <<= 1)
+    {
+        const complex wn = { cos(-flag * 2 * pi / h), sin(-flag * 2 * pi / h) };
+        for (int j = 0; j < len; j += h)
+        {
+            complex w = { 1, 0 };
+            int m = h >> 1;
+            for (int k = j; k < j + m; k++, w = w * wn)
+            {
+                complex u = F[k], t = w * F[k + m];
+                F[k] = u + t, F[k + m] = u - t;
+            }
+        }
+    }
+}
+int main()
+{
+    while (~scanf("%s%s", s1, s2))
+    {
+        int len1, len2, len;
+        memset(a, 0, sizeof(a));
+        memset(b, 0, sizeof(b));
+        memset(ans, 0, sizeof(ans));
+        len1 = (int)strlen(s1) << 1, len2 = (int)strlen(s2) << 1;
+        for (len = 1; len < len1 || len < len2;)
+            len <<= 1;
+        len1 >>= 1, len2 >>= 1;
+        for (int i = 0; i < len1; i++)
+            a[i].r = s1[len1 - 1 - i] - '0';
+        for (int i = 0; i < len2; i++)
+            b[i].r = s2[len2 - 1 - i] - '0';
+        fft(a, len, 1);
+        fft(b, len, 1);
+        for (int i = 0; i < len; i++)
+            a[i] = a[i] * b[i];
+        fft(a, len, -1);
+        for (int i = 0; i < len; i++)
+            ans[i] = int(a[i].r / len + 0.5);
+        for (int i = 0; i < len; i++)
+            ans[i + 1] += ans[i] / 10, ans[i] %= 10;
+        int high = 0;
+        for (int i = len - 1; high == 0 && i >= 0; i--)
+            if (ans[i])
+                high = i;
+        for (int i = high; i >= 0; i--)
+            putchar(ans[i] + '0');
+        putchar('\n');
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/OnlineJudges/lydsy/cur.cpp b/OnlineJudges/hdu/hdu.cpp
similarity index 100%
rename from OnlineJudges/lydsy/cur.cpp
rename to OnlineJudges/hdu/hdu.cpp
diff --git a/OnlineJudges/poj/cur.cpp b/OnlineJudges/poj/cur.cpp
deleted file mode 100644
index e69de29..0000000