#include<fstream.h>
#include<math.h>

ifstream citeste("fact.in");
ofstream scrie("fact.out");

int fact (int n)
	{
	int f=1;
	for (int i=1;i<=n;i++)
		f*=i;
	return f;
	}

int main()
	{
	unsigned long int p,n=1,b=0;
	citeste>>p;
	while (b==0)
		{
		if (fact(n)%pow(10,p)==0) {scrie<<n;b=1;}
		n++;
		}
	citeste.close();
	scrie.close();
	return 0;
	}