#include<cstdio>
using namespace std;
int main()
{
    int n,i,res;
    double t,v,h;
    while(scanf("%lf", &v)==1)
    {
        t=(v/9.8);
        h=4.9*t*t;
        for(n=1;;n++)
        {
            res=5*n-5;
            if(res>h)
                break;
        }
        printf("%d\n",n);
    }
    return 0;
}