#include <bits/stdc++.h>
using namespace std;
int main() {
    int n,a,x;
    cin>>n>>a>>x;
    cout<<n-a*x;
    return 0;
}
/**************************************************************
	Problem: 1599
	User: fuhoubin
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/