N, K = map(int, input().split())
A = list(map(int, input().split()))
M = N * (N - 1)//2 + 5
mod = 10 ** 9 + 7

pre = [0] * M
pre[0] = 1
for i in range(2, N + 1):
    dp = [0] * M
    ndp = [0] * M
    for k in range(M):
        if pre[k] == 0:
            break
        dp[k] += pre[k]
        dp[k+i] -= pre[k]
        dp[k] %= mod
        dp[k+i] %= mod
    
    ndp[0] = dp[0]
    for k in range(1, M):
        ndp[k] = ndp[k - 1] + dp[k]
        ndp[k] %= mod
    
    pre, ndp = ndp, pre

ans = 0
for k in range(K + 1):
    ans += pre[k]
    ans %= mod

print(ans)