int q[635];
Prime(4716,q);
ll@l,@r;
rep[q](p,1,635){
	ll x;
	REP(x,l/+(p*p),(r+1)/(p*p)){///wt(l,x,p,p*p);exit(0);
		ll f[64];
		if(Factor(x,f)==2&&p<f[0]<f[1]&&f[0]*f[1]==x){
			wt(p*p*x);
			exit(0);
		}
	}
}
wt(-1);