#include <iostream>
using namespace std;

int main()
{
    double v;
    while(cin>>v)
    {
        double t = v/9.8;
        double dis = 4.9*t*t;
        int ans = dis/5;
        if(dis-ans*5>0.000000001)
        {
            ans++;
        }
        ans++;
        cout<<ans<<endl;
    }
    return 0;
}