#include<iostream>
#include<cstdio>
#include<cmath>
using namespace std;
int main()
{
    double v;
    while(~scanf("%lf",&v)){
        double t=v/9.8;
        double f=4.9*t*t;
        int N=(f+5.0)/5.0+0.5;
        printf("%d\n",N);
    }
    return 0;
}