#include <bits/stdc++.h>
using namespace std;
int dy4[4] = {-1, 0, +1, 0};
int dx4[4] = {0, +1, 0, -1};
int dy8[8] = {-1, -1, 0, 1, 1, 1, 0, -1};
int dx8[8] = {0, 1, 1, 1, 0, -1, -1, -1};
const long long INF = 1LL << 60;
const long long MOD = 1e9 + 7;
bool greaterSecond(const pair<int, int>& f, const pair<int, int>& s) {
  return f.second > s.second;
}
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
long long lcm(long long a, long long b) { return a / gcd(a, b) * b; }
long long nCr(long long n, long long r) {
  if (r == 0 || r == n) {
    return 1;
  } else if (r == 1) {
    return n;
  }
  return (nCr(n - 1, r) + nCr(n - 1, r - 1));
}
long long nPr(long long n, long long r) {
  r = n - r;
  long long ret = 1;
  for (long long i = n; i >= r + 1; i--) ret *= i;
  return ret;
}
int n, k;
vector<int> a;
long long memo[110][100100];
long long dp(int i, int j) {
  if (j == 0) return 1;
  if (j < 0) return 0;
  if (i == -1) return 0;
  if (memo[i][j] != -1) return memo[i][j];
  long long res = 0;
  res += dp(i - 1, j) % MOD;
  res += dp(i, j - 1) % MOD;
  long long tmp = dp(i - 1, j - a[i] - 1) % MOD;
  res -= tmp;
  if (res < 0) res += MOD;
  return memo[i][j] = res;
}
int main(void) {
  cin >> n >> k;
  a.resize(n);
  for (int i = 0; i < n; i++) cin >> a[i];
  for (int i = 0; i <= n; i++) {
    for (int j = 0; j <= k; j++) {
      memo[i][j] = -1;
    }
  }
  cout << dp(n - 1, k) << endl;
}
