#include <stdio.h>
int main()
{
	double s;
	int i=1;
	int n=0;
	scanf("%lf",&s);
	
	for(double a = 2.0;;i++){
		n = n +a;
		a = a * 0.98;
		if(n >= s) break;
	}
	printf("%d",i);
	
	return 0;
}