#include<iostream>
#include<stdio.h>
using namespace std;

int main()
{
    double v,y,n,t;
    while(scanf("%lf",&v)==1)
    {
        

        t=v/9.8;
        y=4.9*t*t;
        n=(y+5)/5;

        int nt=int(n);
        if(n-nt>=0.5)nt+=1;
        cout<<nt<<endl;
    }
    return 0;

}