#include<iostream>
#include<cstdlib>
#include<cmath>
using namespace std;
#define G 9.8
int main(){
	double v;
	while(cin>>v){
		v = pow(v,2);
		v = v/(2*G) + 5;
		v /= 5;
		cout<<((int)v+1)<<endl;	
	}
	return 0;
}