#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: ljl2
	Language: C++
	Result: Accepted
	Time:7 ms
	Memory:2072 kb
****************************************************************/