#include<bits/stdc++.h>
using namespace std;
int main(){
	int a,b,c,d,e,f;
	cin>>a>>b>>c>>d>>e;
	if(d-e>0){
		cout<<(a+d*c)-(b+e*c)<<endl;
	}else{
		cout<<a-b<<endl;
	}
}