#include<bits/stdc++.h>
using namespace std;
int main(){
    int n,m,k;
    cin>>n>>m>>k;
    cout<<n-m*k;
}
/**************************************************************
	Problem: 1599
	User: zhengzihao
	Language: C++
	Result: Accepted
	Time:8 ms
	Memory:2072 kb
****************************************************************/