#include<stdio.h>
#include<conio.h>
int main()
{
unsigned int p=0, p2=0, p5=0, n, n2,n5;
clrscr();

FILE *f=NULL;
f=fopen("fact.in","r");
fscanf(f,"%d\n",&p);
fclose(f);

n=0;
//printf("Toate bune si frumoase...\np=%d\n",p);

do
{
		n++;
		n2=n;
		while(!(n2%2)){
			p2++;
			n2=n2/2;
		}
		n5=n;
		while(!(n5%5)){
			p5++;
			n5=n5/5;
		}
	}while (p5<p);

n=((!p)?1:n);
//printf("p2=%d, iar p5=%d\nn=%d", p2, p5, n);
f=fopen("fact.out","w");

if ((p2==p) && (p2==p5))
	fprintf(f, "%d", n);
else
	fprintf(f,"-1");
fclose(f);
return 0;
}