#include <bits/stdc++.h>
#define int long long
#define x first
#define y second
#define pb push_back
void debug() {std::cerr << "\n";}
template<class T, class... OtherArgs>
void debug(T &&var, OtherArgs &&... args) {
    std::cerr << std::forward<T>(var) << " ";
    debug(std::forward<OtherArgs>(args)...);
}
#define SZ(x) (int)(x).size()
#define all(x) (x).begin(), (x).end()
using namespace std;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
typedef long long LL;
typedef long double LD;
typedef unsigned long long ULL;
typedef pair<int, int> PII;
const int N = 200010, M = 10000010;
const int P = 1e9 + 7;
LL powmod(LL a, LL b, LL p = P) {LL res = 1 % p; a %= p; assert(b >= 0); for(; b; b >>= 1) { if (b & 1) res = res * a % p; a = a * a % p; } return res; }

int n, m;

void solve() {
    int s = 0;
    for (int i = 0; i < 5; i++) {
        int x, y;
        cin >> x >> y;
        s += x * y;
    }
    s /= 5;
    cin >> n >> m;
    cout << s * n / m << '\n';
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(20);
    int _ = 1;
    // cin >> _;
    while (_--) solve();
}