#include<cstdio>
using namespace std;
double in;
int ans;
double a,b;
int main()
{
    a=0.0;
    b=2.0/0.98;
    scanf("%lf",&in);
    for(ans=1;;ans++)
    {
        a+=b*0.98;
        if(a>in)
        {
            printf("%d",ans);
            break;
        }
    }
}