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18 lines
449 B
C++

#define _CRT_SECURE_NO_WARNINGS
#define _SILENCE_CXX17_C_HEADER_DEPRECATION_WARNING
#include <bits/stdc++.h>
using namespace std;
int a[10050];
int main()
{
int l, m;
cin >> l >> m;
a[0] = 1;
for (int i = 0, x, y; i < m; i++)
cin >> x >> y, a[x]--, a[y + 1]++;
for (int i = 1; i <= l; i++)
a[i] += a[i - 1];
cout << count_if(a, a + l + 1, [](const auto x) { return x > 0; });
return 0;
}