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

	return 0;
}

/**************************************************************
	Problem: 1599
	User: caiqiaoxi
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/