#include<iostream>
#include<cmath>
#include<cstdio>
using namespace std;

int main(){
	
	double v;
	double t,y;
	double N;
	while(cin>>v){
		t=v/9.8;
		y=4.9*pow(t,2.0);
		N = (y+5)/5;
		printf("%.0f\n",N);
	
	}
		
	
}