#include<bits/stdc++.h>
using namespace std;
int main(){
	int n,a,x;
    cin>>n>>a>>x;
    cout<<n-a*x; 
}



/**************************************************************
	Problem: 1599
	User: hulaoshi
	Language: C++
	Result: Accepted
	Time:13 ms
	Memory:2072 kb
****************************************************************/