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

#define in "fact.in"
#define out "fact.out"
#define NMAX (1<<30)
#define minim(a,b) ((a) < (b) ? (a) : (b))


long int N, P;
long int CC, CA;

int main ( void )
{
	freopen ( in, "r", stdin );
	freopen ( out, "w", stdout );

	scanf ( "%ld", &P );
	long int i, cpy;

	CA = 0;	
	
	for ( i = 1; i <= NMAX-5; ++i )
	{
		CC = CA;
		cpy = i;
		while ( cpy%5 == 0 ) cpy /= 5, CC++;
		if ( CC == P ) { printf ( "%ld\n", i ); break; }
		if ( CC > P ) { printf ("-1\n" ); break; }
		CA = CC;
	}
	
	return 0;
}