#include <bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using ll = long long;
using vi = vector<int>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define repr(i, n) for (int i = (int)(n - 1); i >= 0; --i)

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    int a, b, c, d, e;
    cin >> a >> b >> c >> d >> e;
    int ret = a - b;
    if (d - e > 0) ret += (d - e) * c;
    cout << ret << endl;
    return 0;
}