package main

import . "fmt"

func main() {
	sv:=make([]bool,1e7+4)
	pr:=make([]int,0,6e6)
	sv[1]=true
	for i:=3;i<len(sv);i+=2 {
		if sv[i] {
			continue
		}
		if !sv[i-2] {
			pr=append(pr,(i-2)*i)
		}
		for j:=i+i;j<len(sv);j+=i {
			sv[j]=true
		}
	}
	var t int
	Scan(&t)
	for ;t>0;t-- {
		var n int
		Scan(&n)
		lb,ub:=0,len(pr)
		for lb+1<ub {
			mid:=(lb+ub)/2
			if pr[mid]<=n {
				lb=mid
			} else {
				ub=mid
			}
		}
		if pr[lb]<=n {
			Println(pr[lb])
		} else {
			Println(-1)
		}
	}
}