#include <bits/stdc++.h>
using namespace std;
int main(){
	double s;//路程 
	int t;//次数 
	cin>>s;
	double ys=0;//已走路程
	double ks=2;//规定路程 
	while(s>ys){
		ks=ks*0.98;
		ys=ys+ks;
		t++;
	} 
	cout<<t<<endl;
}
/**************************************************************
	Problem: 1460
	User: zengdongxin
	Language: C++
	Result: Time Limit Exceed
****************************************************************/