#include<stdio.h>
int main()
{
unsigned int p=0,p5=0,n,n5;
FILE *f;
f=fopen("fact.in","r");
fscanf(f,"%d",&p);
fclose(f);
n=0;
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);

f=fopen("fact.out","w");
if (p5==p)
	fprintf(f, "%d", n);
else
	fprintf(f,"-1");
fclose(f);
return 0;
}