#include <iostream>
using namespace std;

int main(){
	int c = 1;	
	double t = 2,s = 2,x;
	cin>>x;
	while(s < x){
		t = t * 0.98;
		s = s + t;
		c++;
	}
	
	cout<<c<<endl;
}
/**************************************************************
	Problem: 1460
	User: admin
	Language: C++
	Result: Accepted
	Time:27 ms
	Memory:2072 kb
****************************************************************/