func main()
	var primes: []bool :: sieve(5000000)
	func sieve(n: int): []bool
		var isPrime: []bool :: [true].repeat(n + 1)
		do isPrime[0] :: false
		do isPrime[1] :: false
		for i(2, n + 1)
			if(isPrime[i])
				var j: int :: i * i
				while(j <= n)
					do isPrime[j] :: false
					do j :+ i
				end while
			end if
		end for
		ret isPrime
	end func
	
	var t: int :: cui@inputInt()
	for(1, t)
		do cui@inputInt()
		var p: int :: cui@inputInt()
		var ans: int :: primes[p] ?(1, -1)
		do cui@print("\{ans}\n")
	end for
end func