#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: lvrenxiang
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/