#include <iostream>
using namespace std;

int main() {
	double v;
	while(cin>>v){
		double t=v/9.8;
		double y=4.9*t*t;
		for(int i=1;;i++){
			if(y>5*(i-1)-5&&y<5*i-5){ 
				cout<<i<<endl; break;
			}
		}
	}
	return 0;
}