#include<iostream>
#include<math.h>

int main()
{
	double v;
	
	while( std::cin >> v ){
		int n = 1;
		while( sqrt( ( n * 5 - 5 ) / 4.9 ) * 9.8 < v )n++;
		std::cout << n << std::endl;
	}

 	return 0;
}