def cumsum(inlist):
    s = 0
    outlist = [0]
    for i in inlist:
        s += i
        outlist.append(s)
    return outlist

mod = 10**9+7
n, k = [ int(v) for v in input().split() ]
a_list = [ int(v) for v in input().split() ]

dp_list = [ 0 for i in range(k+1) ]
dp_list[0] = 1

for i in range(n):
    cum_dp_list = cumsum(dp_list)

    new_dp_list = [ 0 for i in range(k+1) ]
    for j in range(k+1):
        r = min(j+1,k+1)
        l = max(0,j-a_list[i]) 
        new_dp_list[j] = cum_dp_list[r] - cum_dp_list[l]
    dp_list = [ i % mod for i in new_dp_list ]

print(dp_list[-1])