N,K = map(int,input().split())
A = list(map(int,input().split()))

P = [0] * 100010

for i in range(N):
	P[A[i]] += 1

A = []

for i in range(1,100010):
	for j in range(min((K + i) // i,P[i])):
		A.append(i)

N = len(A)

B = (1 << K)
C = [0] * 100010
C[0] = 1

mask = (1 << 100010) - 1

for i in range(N):
	C[i + 1] = C[i] | (C[i] << A[i]) 
	C[i + 1] &= mask
if (C[N] & (1 << K)):
	ans = 0
	for i in range(N - 1,-1,-1):
		if (B & C[i]) == 0:
			ans += 1;
		B |= (B >> A[i])
		B &= mask
	print(ans)
else:
	print(-1)