#include <iostream>
#include <vector>
using namespace std;

int main()
{
    vector <long double> c;
    long double m, sum = 0, result = 1;
    while (cin >> m){
        c.push_back(m);
    }
    for (int i = 0; i < c.size()/2; i++){
        sum = c[i] + c[c.size() - 1 - i];
        result *= sum;
    }
    cout << result << endl;
    return 0;
}