#include<bits/stdc++.h>
using namespace std;
int main(){
    double n=2;
	int d=2;
    int ans=0;
    double a;
    cin>>a;
	while(n<a){
	    d=d*(49/50);
		n=n+d;
		ans+=1;
	}
	cout<<ans;
    return 0;
}