#include<bits/stdc++.h>
using namespace std;

int main()
{
	double s;
	int a=0;
	cin>>s;
	double v=2;
	double q=0;
	do
	{
		q=q+v;
		v=v*0.98;
		a=a+1;
	}
	while(q>=s);
	cout<<a;
}