JOI 2017 Yo 2nd

2.cpp

#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <functional>
#include <queue>
#include <cmath>
#include <cstring>

int n, m;
int arr[1010];

int main() {
    std::cin >> n >> m;

    int tmp;
    for(int i = 0; i < m; ++i) {
        std::cin >> arr[i] >> tmp;
    }

    std::sort(arr, arr + m, std::greater<int>());

    int ans = 0;
    for(int i = 0; i < m - 1; ++i) {
        ans += std::max(n - arr[i], 0);
    }

    std::cout << ans << std::endl;
}