#include <iostream>
using namespace std;

int main(void)
{
    double v, t, y, N;
    
    while(cin >> v)
    {
        t = v / 9.8;
        y = 4.9 * t * t;
        N = (y+5)/5;
        cout << (int)++N << endl;
    }
    return 0;
}