#include <stdio.h>
#include <atcoder/all>
#include <bits/stdc++.h>
using namespace std;
using namespace atcoder;
using mint = modint998244353;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf32 1000000001
#define Inf64 4000000000000000001



int main(){
	
	int a,b,c,d,e;
	cin>>a>>b>>c>>d>>e;
	
	int ans = a-b;
	
	if(d-e>=0)ans += c * (d-e);
	
	cout<<ans<<endl;
	
	return 0;
}