#include<stdio.h>

long k[]={1,5,25,125,625,3125,15625,78125,625000,15625000,78125000};

long putere (long n)
{
	long i=1,s;
	s=0;
	while(k[i]<=n)
		{
			s=s+n/k[i];
			++i;
		}
	return s;
}
	
int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	
	long p,i,j,n;
	
	scanf("%ld",&p);

	
	for(n=1;;n++)
		if(putere(n)==p)
			break;
	printf("%ld",n);
	printf("\n");
	return 0;
}