#include <stdio.h>

int main ()
{
	double sum=2.0,a=2.0,lon;
	int i=1;
	scanf ("%d",&lon);
	while (sum<lon)
	{
		a=a*0.98; 
		sum=sum+a;
		i++;
	}
	printf ("%d",i);
	return 0;
 }