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