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

int main(){
	double n;
	int k = 0;
	int out[1000];
	while(cin >> n){
		double v, t;
		for(int i = 1; i < 1000; i++){	
			t = sqrt((5*i-5)/4.9);
			v = 9.8*t;
			if(v >= n){
				out[k] = i;
				break;
			}
		}
		k++;
	}
	for(int i = 0; i < k; i++){
		cout << out[i] << endl;
	}
}