import std.conv, std.functional, std.range, std.stdio, std.string;
import std.algorithm, std.array, std.bigint, std.complex, std.container, std.math, std.numeric, std.regex, std.typecons;
import core.bitop;

class EOFException : Throwable { this() { super("EOF"); } }
string[] tokens;
string readToken() { for (; tokens.empty; ) { if (stdin.eof) { throw new EOFException; } tokens = readln.split; } auto token = tokens.front; tokens.popFront; return token; }
int readInt() { return readToken.to!int; }
long readLong() { return readToken.to!long; }
real readReal() { return readToken.to!real; }

bool chmin(T)(ref T t, in T f) { if (t > f) { t = f; return true; } else { return false; } }
bool chmax(T)(ref T t, in T f) { if (t < f) { t = f; return true; } else { return false; } }

int binarySearch(alias pred, T)(in T[] as) { int lo = -1, hi = cast(int)(as.length); for (; lo + 1 < hi; ) { const mid = (lo + hi) >> 1; (unaryFun!pred(as[mid]) ? hi : lo) = mid; } return hi; }
int lowerBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a >= val)); }
int upperBound(T)(in T[] as, T val) { return as.binarySearch!(a => (a > val)); }


enum MO = 10L^^9 + 7;

int N, K;
int[] A;

void main() {
  try {
    for (; ; ) {
      N = readInt();
      K = readInt();
      A = new int[N];
      foreach (i; 0 .. N) {
        A[i] = readInt();
      }
      
      auto dp = new long[K + 1];
      dp[0] = 1;
      foreach (i; 0 .. N) {
        auto dpSum = new long[K + 2];
        foreach (k; 0 .. K + 1) {
          dpSum[k + 1] = (dpSum[k] + dp[k]) % MO;
        }
        foreach (k; 0 .. K + 1) {
          dp[k] = (dpSum[k + 1] - dpSum[max(k - i, 0)]) % MO;
        }
      }
      long ans;
      foreach (k; 0 .. K + 1) {
        ans += dp[k];
        ans %= MO;
      }
      ans = (ans % MO + MO) % MO;
      writeln(ans);
    }
  } catch (EOFException e) {
  }
}