#include <stdio.h>
#include <math.h>
int putere(long n)
{
	int t=0;
	while (n>0)
		{
			n/=5;
			t++;
		}
	return t;
}

int main()
{
	long p,i;
	FILE *f,*g;
	int nr=0;
	
	f=fopen("fact.in","r");
	fscanf(f,"%li",&p);
	fclose(f);
	
	for (i=5; ; i+=5)
		{
			nr=nr+putere(i);
			if (nr>=p) break;
		}

	g=fopen("fact.out","w");
	if (p<5) fprintf(g,"%i",0);
	else 
		if (nr>p) fprintf(g,"%i",-1);
		else fprintf(g,"%li",i);
	fclose(g);
	return 0;
}