#include <bits/stdc++.h>
#define rep(i, n) for (int i = 0; i < n; ++i)
typedef long long ll;
using namespace std;

int main() {
    cin.tie(0)->sync_with_stdio(0);

    int A, B, C, D, E;
    cin >> A >> B >> C >> D >> E;

    int ans = max(A - B, A - B + C * (D - E));
    cout << ans << "\n";

    return 0;
}