#include <bits/stdc++.h>

using namespace std;

int main()
{
    double m,t,s,ans;

    cin >> m >> t >> s;
    if(t==0){
        cout << "0";
    }
    else {
    int ans = m -s/t;
    max(ans,0);
    cout << ans;
    }
    return 0;
}

我觉得某些情况不用-1啊