#include <stdio.h>
int main()
{
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	int n,k,r,s,i,gasit=0,salvat;
	scanf("%d",&k);
	if (k<0)
		printf("-1");
	for (i=1; i<=1000000 && gasit==0; i++)
	{
		r=5;
		salvat=i;
		s=0;
		while (r<=i)
		{
			s=s+i/r;
			r=r*5;
		}
		if (s==k) {
			gasit=1;
			printf("%d",salvat);
		}
	}
	return 0;
}