#include<iostream>
using namespace std;
int main()
{
long double v,n;
int N;
while(cin>>v)
{
n=0;
N=0;
n=4.9*(v/9.8)*(v/9.8)/5+1;
N=n*10;	
if(N%10==0)
{
	cout<<N/10<<endl;
}
else if(N%10!=0)
{
	cout<<N/10+1<<endl;
}
}
return 0;
}