#include <iostream>
#include <math.h>
using namespace std;

int main()
{
    double num, t;
	int n;
	while( cin >> num ) {
		t = 4.9  * ( num / 9.8 ) * ( num / 9.8 );	
		n = ceil( ( t + 5 ) / 5 );
	    cout << n << endl;
	}

        return 0;
}
  