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

# import random
# N = 100
# K = 10**5
# A = [K] * N

if sum(A) < K:
  print(0)
  exit(0)

t0 = [0] * (K+1)
t0[0] = 1

M = 10**9 + 7
for i in range(N):
    a = A[i]
    t1 = [0] * (K+1)
    st0 = [0]
    for t in t0:
        st0.append((t + st0[-1]) % M)
    for k in range(K+1):
        l = max(0, k-a)
        t1[k] = (st0[k+1] - st0[l]) % M
    t0 = t1

print(t0[K])
