题解 | 校门外的树

#include <iostream>
using namespace std;

int main() {
    int l, m, li, ri;
    cin >> l >> m;
    int arr[10001] = { 0 };
    while (cin >> li >> ri)
    {
        for (int i = 0; i <= l; i++)
        {
            if (i >= li && i <= ri) arr[i] = 1;
        }
    }
    int count = 0;
    for (int i = 0; i <= l; i++)
    {
        if (!arr[i]) count++;
    }
    cout << count;
    return 0;
}
// 64 位输出请用 printf("%lld")