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

using namespace std;

int main(void){
    double v;
    
    while (cin>>v)
    {
        double n,k;
        n = (4.9*(v/9.8)*(v/9.8)+5)/5;
        k=n-(int)n;
        if(0==k);
        else {n++;}
        cout<<(int)n<<endl;
    }
    return 0;
}