#include<stdio.h>
int zero(int n)
{
	int r=0;
	while(n)
		r+=(n/=5);
	return r;
}
int caut(int p)
{
	int i,pas=(1<<10);
	for(i=0; pas; pas>>=1)
		if(zero(i+pas)<=p-1)
			i+=pas;
	if(zero(i+1)!=p)
		return -1;
	return i+1;
}
int main()
{
	int n,p;
	freopen("fact.in","r",stdin);
	freopen("fact.out","w",stdout);
	scanf("%d",&p);
	printf("%d\n",caut(p));
	return 0;
}