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




/**************************************************************
	Problem: 1599
	User: fuyijun
	Language: C++
	Result: Accepted
	Time:9 ms
	Memory:2072 kb
****************************************************************/