#include<fstream>
using namespace std;
ifstream fin("fact.in");
ofstream fout("fact.out");

int catecifre(int cifra)
{
	int nrc;
	while(cifra)
	{
		cifra = cifra / 10;
		nrc++;
	}
	return nrc;
}
int factorial(int number)
{
	int temp;
    if(number <= 1) 
		return 1;
	temp = number * factorial(number - 1);
    return temp;

}
int main()
{
	int p, n = 1, gasit = 0;
	fin >> p;
	while(gasit == 0)
	{
		
		if(catecifre(factorial(n)) == p)//daca cate cifre are n! == p 
			gasit = 1;
		    else
				n++;
		/*if( gasit == 0 && catecifre(factorial(n)) != p && catecifre(factorial(n)) > 100000000 )//daca inca nu am gasit un factorial de n sa aiba p cifre si cifrele factorialului n > pow(10,8) facem break si d = 1;
			{
				d = 1;
				break;
		    } */
	}   
	
		fout << n;
	
	return 0;
	fin.close();
	fout.close();
}