#dp[i][j] denotes number of ways to distribute j candies among first i
l=input().split()
n=int(l[0])
k=int(l[1])
l=input().split()
li=[int(i) for i in l]
dp=[[0 for i in range(k+1)]for i in range(n+1)]
for i in range(n+1):
    dp[i][0]=1
for i in range(1,k+1):
    dp[0][i]=0
pref=[0 for i in range(k+1)]
sumi=0
for i in range(k+1):
    sumi+=dp[0][i]
    pref[i]=sumi
    pref[i]%=1000000007
for i in range(1,n+1):
    for j in range(1,k+1):
        howmany=li[i-1]
        left=max(0,j-howmany)
        right=j
        if(left==0):
            dp[i][j]=pref[j]
        else:
            dp[i][j]=pref[j]-pref[left-1]
        dp[i][j]%=1000000007
    sumi=0
    for j in range(k+1):
        sumi+=dp[i][j]
        pref[j]=sumi
        pref[j]%=1000000007
print(dp[n][k])
