diff --git a/OnlineJudges/lydsy/1045.cpp b/OnlineJudges/lydsy/1045.cpp
new file mode 100644
index 0000000..02708fb
--- /dev/null
+++ b/OnlineJudges/lydsy/1045.cpp
@@ -0,0 +1,32 @@
+#include <cstdio>
+#include <cctype>
+#include <cstring>
+#include <algorithm>
+#include <numeric>
+typedef long long int64;
+template <typename T> inline void readInt(T &x)
+{
+    int ch = x = 0;
+    while (!isdigit(ch = getchar()));
+    for (; isdigit(ch); ch = getchar()) x = x * 10 + ch - '0';
+}
+int64 *A, *C;
+int main()
+{
+    int n;
+    readInt(n);
+    A = new int64[n + 10];
+    C = new int64[n + 10];
+    memset(A, 0, sizeof(int64)*(n + 10));
+    memset(C, 0, sizeof(int64)*(n + 10));
+    for (int i = 0; i < n; i++) readInt(A[i]);
+    int64 tmp = std::accumulate(A, A + n, 0ll) / n;
+    for (int i = 1; i < n; i++)
+        C[i] = C[i - 1] + tmp - A[i];
+    std::nth_element(C, C + (n >> 1), C + n);
+    tmp = 0;
+    for (int i = 0; i < n; i++)
+        tmp += std::abs(C[i] - C[n >> 1]);
+    printf("%lld", tmp);
+    return 0;
+}
\ No newline at end of file
diff --git a/OnlineJudges/lydsy/1050.cpp b/OnlineJudges/lydsy/1050.cpp
new file mode 100644
index 0000000..e035752
--- /dev/null
+++ b/OnlineJudges/lydsy/1050.cpp
@@ -0,0 +1,46 @@
+#include <cstdio>
+#include <cstring>
+#include <algorithm>
+struct edge
+{
+    int from, to, len;
+    bool operator<(const edge &rhs) const { return len < rhs.len; };
+}edges[5010];
+int fa[510];
+int Find(int x) { return fa[x] == -1 ? x : fa[x] = Find(fa[x]); }
+int gcd(int a, int b) { return b == 0 ? a : gcd(b, a % b); }
+int n, m, s, t, ans1, ans2, flag;
+int main()
+{
+    scanf("%d%d", &n, &m);
+    for (int i = 0; i < m; i++) scanf("%d%d%d", &edges[i].from, &edges[i].to, &edges[i].len);
+    std::sort(edges, edges + m);
+    scanf("%d%d", &s, &t);
+    ans1 = edges[m - 1].len, ans2 = edges[0].len;
+    for (int i = 0, mn, mx; i < m; i++)
+    {
+        memset(fa, -1, sizeof(fa));
+        mn = edges[i].len;
+        for (int j = i, fx, fy; j < m; j++)
+        {
+            mx = edges[j].len;
+            fx = Find(edges[j].from), fy = Find(edges[j].to);
+            if (fx != fy) fa[fx] = fy;
+            if (Find(s) == Find(t))
+            {
+                if (ans1 * mn > ans2 * mx) ans1 = mx, ans2 = mn;
+                flag = 1;
+                break;
+            }
+        }
+    }
+    if (!flag) printf("IMPOSSIBLE");
+    else
+    {
+        int k = gcd(ans1, ans2);
+        ans1 /= k, ans2 /= k;
+        if (ans2 == 1) printf("%d", ans1);
+        else printf("%d/%d", ans1, ans2);
+    }
+    return 0;
+}
\ No newline at end of file
diff --git a/OnlineJudges/lydsy/1214.cpp b/OnlineJudges/lydsy/1214.cpp
new file mode 100644
index 0000000..c272dab
--- /dev/null
+++ b/OnlineJudges/lydsy/1214.cpp
@@ -0,0 +1 @@
+int main() {}
\ No newline at end of file
diff --git a/OnlineJudges/lydsy/2818.cpp b/OnlineJudges/lydsy/2818.cpp
new file mode 100644
index 0000000..441ed3c
--- /dev/null
+++ b/OnlineJudges/lydsy/2818.cpp
@@ -0,0 +1,29 @@
+#include <cstdio>
+typedef long long int64;
+const int maxn = 10000010;
+int n, phi[maxn], prime[700010], pcnt;
+int64 sum[maxn];
+bool notPrime[maxn];
+int main()
+{
+    scanf("%d", &n);
+    phi[1] = 1;
+    for (int i = 2; i <= n; i++) if (!phi[i])
+        for (int j = i; j <= n; j += i)
+        {
+            if (!phi[j]) phi[j] = j;
+            phi[j] = phi[j] / i * (i - 1);
+        }
+    for (int64 i = 2; i <= n; i++) if (!notPrime[i])
+        for (int64 j = i * i; j <= n; j += i)
+            notPrime[j] = true;
+    for (int i = 2; i <= n; i++)
+        if (!notPrime[i])
+            prime[pcnt++] = i;
+    for (int i = 1; i <= n; i++) sum[i] = sum[i - 1] + phi[i];
+    int64 ans = 0;
+    for (int i = 0; i < pcnt; i++)
+        ans += (sum[n / prime[i]] << 1) - 1;
+    printf("%lld", ans);
+    return 0;
+}
\ No newline at end of file
diff --git a/OnlineJudges/lydsy/3293.cpp b/OnlineJudges/lydsy/3293.cpp
new file mode 100644
index 0000000..02708fb
--- /dev/null
+++ b/OnlineJudges/lydsy/3293.cpp
@@ -0,0 +1,32 @@
+#include <cstdio>
+#include <cctype>
+#include <cstring>
+#include <algorithm>
+#include <numeric>
+typedef long long int64;
+template <typename T> inline void readInt(T &x)
+{
+    int ch = x = 0;
+    while (!isdigit(ch = getchar()));
+    for (; isdigit(ch); ch = getchar()) x = x * 10 + ch - '0';
+}
+int64 *A, *C;
+int main()
+{
+    int n;
+    readInt(n);
+    A = new int64[n + 10];
+    C = new int64[n + 10];
+    memset(A, 0, sizeof(int64)*(n + 10));
+    memset(C, 0, sizeof(int64)*(n + 10));
+    for (int i = 0; i < n; i++) readInt(A[i]);
+    int64 tmp = std::accumulate(A, A + n, 0ll) / n;
+    for (int i = 1; i < n; i++)
+        C[i] = C[i - 1] + tmp - A[i];
+    std::nth_element(C, C + (n >> 1), C + n);
+    tmp = 0;
+    for (int i = 0; i < n; i++)
+        tmp += std::abs(C[i] - C[n >> 1]);
+    printf("%lld", tmp);
+    return 0;
+}
\ No newline at end of file
diff --git a/OnlineJudges/lydsy/3816.cpp b/OnlineJudges/lydsy/3816.cpp
new file mode 100644
index 0000000..c272dab
--- /dev/null
+++ b/OnlineJudges/lydsy/3816.cpp
@@ -0,0 +1 @@
+int main() {}
\ No newline at end of file