题解 | 剩下的树

#include <iostream>
using namespace std;

int main() {
    int m, n;
    cin >> m >> n;
    int sum = m + 1;

    int x[m + 1];
    for (int i = 0; i <= m; i++)
        x[i] = 1;
    int a, b;
    while (n--) {
        cin >> a >> b;
        for (int i = a; i <= b; i++)
            x[i] = 0;
    }
    int co = 0;
    for (int i = 1; i <= m; i++) {
        if (x[i] != 0) co++;
    }
    cout << co + 1;
}
// 64 位输出请用 printf("%lld")