
#include<iostream>
#include<stdio.h>
#include<algorithm>

using namespace std;

int main(){
	double  v;

	while(scanf("%lf",&v) != EOF){

		cout << (int)((4.9/5)*((v*v)/(9.8*9.8)) + 1 + 0.9)<< endl;
	}
		return 0;
}