#include <bits/stdc++.h>

using namespace std;

int m, t, s, ans;

int main()
{
    cin >> m >> t >> s;

    if (t == 0)
    {
        cout << m;
        return 0;
    }

    ans = max(0, m - (s / t + s % t));
    cout << ans << endl;

    return 0;
}