#include<iostream>
#include<cmath>
using namespace std;
int main(){
	double x;
	while(cin >>x){
		for(int i=1;;i++){
			double hight=5*i-5,v=sqrt(4*4.9*hight);
			if(v>=x){cout <<i<<endl;break;}
		}
	}
	return 0;
}