#define _CRT_SECURE_NO_WARNINGS
#include <stdio.h>

unsigned int zero_count(unsigned int n)
{
	unsigned int count = 0;
	while (n % 10 == 0)
	{
		n = n / 10;
		count++;
	}
	return count;
}

int main()
{
	FILE* f = fopen("fact.in", "rt");
	unsigned int n, p=1, i=2;
	
	fscanf(f, "%u", &n);

	while (zero_count(p) != n)
	{
		p = p * i;
		i++;
	}

	f = fopen("fact.out", "wt");

	fprintf(f, "%d\n", i-1);
	fflush(stdout);

	fclose(f);
	return 0;
}