#include <bits/stdc++.h>
#include <map>
#include <math.h>
#include <string>
#include <string.h>
#include <vector>
#include <queue>
#include <algorithm>
#include <set>
using namespace std;
using ll = long long;
const ll dx[4] = {1,0,-1,0};
const ll dy[4] = {0,1,0,-1};
ll mod(ll x, ll m){return x & m;}
ll modinv(ll a, ll m) {
    ll b = m, u = 1, v = 0;
    while (b) {
        ll t = a / b;
        a -= t * b; swap(a, b);
        u -= t * v; swap(u, v);
    }
    u %= m;
    if (u < 0) u += m;
    return u;
}
ll modpow(ll a, ll n, ll m) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * a % m;
        a = a * a % m;
        n >>= 1;
    }
    return res;
}
ll yaku(ll x){
    ll cnt = 0;
    for(int i = 1; i * i <= x; i++){
        if(x % i == 0){
            if(i == x / i) cnt++;
            else cnt += 2;
        }
    }
    return cnt;
}
ll modwaru(ll a, ll b, ll m){
    a %= m;
    return a * modinv(b, m) % m;
}
ll gcd(ll x, ll y){
    if(x % y == 0)return y;
    else return gcd(y, x % y); 
}

int main(){
    ll A, B, C, D, E, kosuu = 0, ans = 0 ,X;
    cin >> A >> B >> C >> D >> E;
    X = D;
    kosuu = A * (B - C);
    bool b = true;
    while(kosuu > 0){
        if(E <= X){
            if(!b)X -= E;
            if(X < 0) X = 0;
            if(b)ans += X * min(kosuu, (ll)9);
            else ans += X * min(kosuu, (ll)10);
            if(!b)kosuu -= 10;
            else kosuu -= 9;
            b = false;
        }else{
            ans += X * min(kosuu, (ll)10);
            kosuu -= 10;
        }
    }
    cout << ans << endl;
}