#define _USE_MATH_DEFINES
 
#include <iostream>
#include <cstdio>
#include <algorithm>
#include <string>
#include <vector>
#include <cmath>

using namespace std;

int main(){
	double v;
	
	while( cin >> v ){
		double t=v/9.8;
		double y=4.9*t*t;
		double n=0;
		while(1){
			if(5*n-5 > y){
				break;
			}
			n=n+1;
		}
		cout << n << endl;
	}
	return 0;
}