#include <stdio.h>
#include <stdlib.h>


int val(int p)
{
	int fact = 2,count=0,i=3;
	if (p == 0)
	{
		return 1;
	}
	while (count!=p)
	{
		fact = fact*i;
		if (fact % 10 == 0)
		{
			count++;
			fact = fact / 10;
		}
		i++;
	}
	return i-1;
}

int main()
{
	FILE *A = fopen("fact.in", "r");
	FILE *B = fopen("fact.out", "w");
	int p;
	fscanf(A, "%d", &p);
	fprintf(B, "%d", val(p));
}