#include <cstdio>
int main()
{
    double v,h;
    double i=1;
    while(~scanf("%lf",&v))
    {
        h=v*v/(9.8*2);
        while(1)
        {
            if((i-1)*5>=h)
            break;
            i+=1;
        }
        //int j=(int)i;
        printf("%.0lf\n",i);
    }
    return 0;
}