#include<stdio.h>
int zero(int n)
{
	int r=0;
	
	while(n)
	{
		r+= n/5;
		n/=5;
	}
	return r;
}
int cautbin(int p)
{
	int i,pas=1<<30;
	for(i=0;pas;pas>>=1)
		if (zero(i+pas)<p)
			i+=pas;
	if (zero(i+1)!=p) return -1;
	return 1+i;
}
int main()
{
	int p;
	freopen("fact1.in","r",stdin);
	freopen("fact1.out","w",stdout);
	scanf("%d",&p);
	printf("%d",cautbin(p));
	return 0;
}