#include<iostream>
#include<stdio.h>
#include<math.h>
using namespace std;

int main(){
	float input;
	while(scanf("%f", &input) != EOF){
		int ans = 1;
		while(1){
			float time = sqrt((5*ans - 5) / 4.9);
			float speed = time * 9.8;
			if(input < speed) break;
			ans++;
		}
		cout << ans << endl;
	}
}