#include <iostream>
#include <math.h>
#include <vector>
#include <utility>

using std::vector;
using std::cout;
using std::endl;
using std::cin;

int main()
{
    int v, t;

    while(cin >> v && cin >> t)
    {
        cout << 2*v*t << endl;
    }

    return 0;
}