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

int main() {
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    
    int a, b, c, d, e;
    cin >> a >> b >> c >> d >> e;
    int kosuu = (b - c) * a;
    int ans = 0;
    int cost = -1;
    rep(i, kosuu) {
        if(i == 0) cost = d;
        else if (i % 10 == 9 && e <= cost)
            cost -= e;
        ans += cost;
    }
    cout << ans << endl;
    return 0;
}