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) { } }