/**
*    author:  shu8Cream
*    created: 31.03.2021 20:51:18
**/

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

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    ll a,b,c,d,e;
    cin >> a >> b >> c >> d >> e;
    ll ans = 0;
    ll x = d;
    for(ll i=1; i<=a*(b-c); i++){
        if(i==1) ans+=x;
        else{
            if(i%10!=0) ans+=x;
            if(i%10==0 && e<=x){
                x-=e;
                ans+=x;
            }
            if(i%10==0 && e>x) ans+=x;
        }
    }
    cout << ans << endl;
}