#include <stdio.h>
using namespace std;
int main ()
{
    double v,t,y,n;
    while(scanf("%lf",&v)!=EOF){
        n=0;
        y=4.9*(v/9.8)*(v/9.8);
        if((int)y%5==0){
            n=y/5+1;
        }
        else n=y/5+2;
        printf("%d\n",(int)n);
    }
    return 0;
}