#include<stdio.h>
#include<math.h>
int main ()
{
	FILE *in, *out;

	int p, i=0, t, j;
	unsigned long n, pr;

	in = fopen("fact.in", "rt");
	out = fopen("fact.out", "wt");

	fscanf(in, "%d", &p);

		  n = pow(10,p);

	do
	{
		i++;
		pr=1;

		for(j=1;j<=i;++j)
			pr = pr * j;

		if(pr%n==0)
			t=1;
	}
	while(t!=1);

	fprintf(out, "%d", i);

 	fcloseall();

	return (0);
}