/*

Author: Haze

2024/5/23

*/

#include <bits/stdc++.h>

#define irep(i, l, r) for(int i = (l); i <= (r); ++ i)
#define drep(i, r, l) for(int i = (r); i >= (l); -- i)
#define IOS ios::sync_with_stdio(false), cin.tie(nullptr);
using namespace std;
typedef long long ll;

inline ll readL() {
    ll s = 0;
    bool fl = false;
    char ch = (char) getchar();
    while (!isdigit(ch)) {
        if (ch == '-')fl = true;
        ch = (char) getchar();
    }
    while (isdigit(ch)) {
        s = s * 10 + (ch ^ 48);
        ch = (char) getchar();
    }
    return fl ? -s : s;
}

inline int read() {
    return (int) (readL());
}

const int mod = 1000000000 + 7;
const int itinf = 1000000999;
const ll llinf = 2e18;
const int N = 5000099;


void solve() {
    ll sums = 0;

    irep(i, 0, 4) {
        int a, b;
        cin >> a >> b;

        sums += a * b;
    }
    sums /= 5;
  
    int a, b;
    cin >> a >> b;
    cout << sums * a / b << endl;

}

int main() {
    // IOS
    int T = 1;
    while (T--) {
        solve();
    }
    return 0;
}