#include <iostream>
#include <cmath>
using namespace std;
 
int main() 
{
   double k = 1, T = 10, N, S = 10;
   cin >> N;
   while (N > T) {
       S = S * 1.1;
       T = S + T;
       k++;
   }
   cout << k;
   return 0;
}