#include <bits/stdc++.h>

using namespace std;

int N;
int h1, m1, h2, m2;

int sum(int h1, int m1, int h2, int m2)
{
    int total = 0;
    int sleep = (h2 * 60 + m2) - (h1 * 60 + m1);
    if (sleep < 0)
    {
        sleep += 24 * 60;
    }
    total += sleep;
    return total;
}
int main()
{
    freopen("r", "sleep.in", stdin);
    freopen("w", "sleep.out", stdout);
    cin >> N;
    int total = 0;
    while (N--)
    {
        char c;
        cin >> h1 >> c >> m1 >> h2 >> c >> m2;
        total += sum(h1, m1, h2, m2);
    }
    cout << total << endl;
    fclose(stdin);
    fclose(stdout);
    return 0;
}

上面是代码，文件读写有，但是没有输出文件，应该是没有读到文件（我试过fin了）