#nullable enable #region var (_input, _iter) = (Array.Empty(), 0); T I() where T : IParsable { while (_iter >= _input.Length) (_input, _iter) = (Console.ReadLine()!.Trim().Split(' '), 0); return T.Parse(_input[_iter++], null); } #endregion var n = I(); var m = I(); var g = Enumerable.Range(0, n).Select(_ => new List()).ToArray(); for (var i = 0; i < m; i++) { var u = I() - 1; var v = I() - 1; g[u].Add(v); g[v].Add(u); } var s = I(); var t = I(); var a = I() - 1; var b = I() - 1; var invz = new long[n + 1]; for (var i = 1; i <= n; i++) invz[i] = Power(i, Matrix.p - 2); var matrix = new Matrix(new int[n, n]); for (var i = 0; i < n; i++) { var q = invz[g[i].Count]; foreach (var j in g[i]) matrix[i, j] = q; } long F(long tl, int vl, long tr, int vr) { var v = new Matrix(new int[1, n]); v[0, vl] = 1; v *= matrix.Power(tr - tl); return v[0, vr]; } var ap = F(1, 0, t, b) * F(t, b, s, a) % Matrix.p; var aq = F(1, 0, s, a); var ans = ap * Power(aq, Matrix.p - 2) % Matrix.p; Console.WriteLine(ans); static long Power(long v, long p) { var (res, k) = (1L, v); while (p > 0) { if ((p & 1) > 0) res = res * k % Matrix.p; k = k * k % Matrix.p; p >>= 1; } return res; } readonly struct Matrix { long[,] V { get; init; } public long this[int i, int j] { get => V[i, j]; set { V[i, j] = Mod(value); } } public int X => V.GetLength(0); public int Y => V.GetLength(1); public const int p = 998244353; static long Mod(long v) { var res = v % p; if (res < 0) res += p; return res; } public Matrix(int[,] matrix) { var (x, y) = (matrix.GetLength(0), matrix.GetLength(1)); var v = new long[x, y]; for (var i = 0; i < x; i++) for (var j = 0; j < y; j++) v[i, j] = Mod(matrix[i, j]); V = v; } public static implicit operator Matrix(int[,] matrix) => new(matrix); static Matrix With(long[,] matrix) => new(){ V = matrix }; public static Matrix IdentityMatrix(int size) { var v = new long[size, size]; for (var i = 0; i < size; i++) v[i, i] = 1; return With(v); } public static Matrix operator +(Matrix a, Matrix b) { var (v, va, vb, x, y) = (new long[a.X, a.Y], a.V, b.V, a.X, a.Y); for (var i = 0; i < x; i++) for (var j = 0; j < y; j++) { var sum = va[i, j] + vb[i, j]; if (sum > p) sum -= p; v[i, j] = sum; } return With(v); } public static Matrix operator *(Matrix a, Matrix b) { var (v, va, vb, x, y, z) = (new long[a.X, b.Y], a.V, b.V, a.X, b.Y, a.Y); for (var i = 0; i < x; i++) for (var k = 0; k < z; k++) { var c = va[i, k]; if (c != 0) for (var j = 0; j < y; j++) v[i, j] += vb[k, j] * c % p; } for (var i = 0; i < x; i++) for (var j = 0; j < y; j++) v[i, j] = Mod(v[i, j]); return With(v); } public static Matrix operator *(Matrix a, long k) { var (v, va, x, y) = (new long[a.X, a.Y], a.V, a.X, a.Y); for (var i = 0; i < x; i++) for (var j = 0; j < y; j++) v[i, j] = va[i, j] * k % p; return With(v); } public Matrix Power(long k) { var c = IdentityMatrix(X); var c2 = this; while (k > 0) { if ((k & 1) > 0) c *= c2; c2 *= c2; k >>= 1; } return c; } }