#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define int ll
#define _FastIO ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0)
#define pii pair<int , int>
#define pb emplace_back
#define endl '\n'
#define all(x) x.begin() , x.end()
#define rall(x) x.rbegin() , x.rend()
#define F first
#define S second
const int mod = 1e9 + 7;
const int MAXX = 1e3 + 5;

int a , b , c , d , e;

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