#include <stdio.h>
#include <stdlib.h>
  
int main(int argc, char *argv[]) {
	float x,y=2;
	int N=1;
	float path=2;
	scanf("%f",&x);
	if(x<=2)
	    printf("1"); 
	    
	else
	{
		for(y=2;y<x;)
	    {
	    path=path*0.8;
	    y=y+path;
		N=N+1;
	    }
	    printf("%d",&N);
	}
	
	return 0;
}