#include<cstdio>
int zero(int n)
{
	int nr=0;
	while(n)
	{
		nr+=(n/5);
		n/=5;
		
	}
	return nr;
}

int cb(int p)
{
	
	int pas=(1<<30),i;
	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 p;
	freopen("factorial.in","r",stdin);
	freopen("factorial.out","w",stdout);
	
	scanf("%d",&p);
	
	printf("%d",cb(p));
	return 0;
}