/* q^N = Sum S(n, i) (q)_i q^M = Sum S(m, j) (q)_j Sum Sum[i + j = k] S(n, i) S(m, j) (q)_k */ import std.conv, std.functional, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.container, std.math, std.numeric, std.range, 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; enum Q = (MO + 1) / 2 * 5 % MO; enum LIM = 5010; int N, M; void main() { auto S = new long[][LIM]; foreach (n; 0 .. LIM) { S[n] = new long[n + 1]; S[n][0] = 0; S[n][n] = 1; foreach (k; 1 .. n) { S[n][k] = (S[n - 1][k - 1] + k * S[n - 1][k]) % MO; } } try { for (; ; ) { N = readInt(); M = readInt(); auto coef = new long[N + M + 1]; foreach (i; 0 .. N + 1) foreach (j; 0 .. M + 1) { coef[i + j] += S[N][i] * S[M][j]; coef[i + j] %= MO; } debug { writeln("coef = ", coef); } long ans; long qq = 1; foreach (k; 0 .. N + M + 1) { ans += coef[k] * qq; ans %= MO; qq = (qq * (Q - k)) % MO; } ans = (ans % MO + MO) % MO; writeln(ans); } } catch (EOFException e) { } }