#include <iostream>
#include <iomanip>
#include <math.h>
#include <utility>
#include <vector>
#include <cstdlib>
#include <algorithm>
#include <climits>
using namespace std;

int main(){
	int x;
	while(cin>>x){
		double h = (5+4.9*x/9.8*x/9.8)/5;
		int y=0;
		while(y<h) y++;
		cout << y << endl;
	}
	return 0;
}