import sys
from itertools import permutations,accumulate
sys.setrecursionlimit(10**7)
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())
def LI(): return list(map(int,sys.stdin.readline().rstrip().split()))
def LI2(): return list(map(int,sys.stdin.readline().rstrip()))
def S(): return sys.stdin.readline().rstrip()
def LS(): return list(sys.stdin.readline().rstrip().split())
def LS2(): return list(sys.stdin.readline().rstrip())


N,K = MI()
A = LI()
mod = 10**9+7

dp = [[0]*(K+1) for _ in range(N+1)]
for j in range(K+1):
    dp[0][j] = 1
for i in range(1,N+1):
    for j in range(K+1):
        if j >= i:
            dp[i][j] = dp[i-1][j]-dp[i-1][j-i]
        else:
            dp[i][j] = dp[i-1][j]
    X = [0]*(K+1)
    for j in range(K+1):
        if j == 0:
            X[j] = dp[i][j]
        else:
            X[j] = X[j-1]+dp[i][j]
            X[j] %= mod
    dp[i] = X

print(dp[-1][-1])