import std.conv, std.functional, std.range, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.bitmanip, std.complex, std.container, std.math, std.mathspecial, 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)); } struct ModInt(uint M_) { import std.conv : to; alias M = M_; uint x; this(ModInt a) { x = a.x; } this(uint x_) { x = x_ % M; } this(ulong x_) { x = cast(uint)(x_ % M); } this(int x_) { x = ((x_ %= cast(int)(M)) < 0) ? (x_ + cast(int)(M)) : x_; } this(long x_) { x = cast(uint)(((x_ %= cast(long)(M)) < 0) ? (x_ + cast(long)(M)) : x_); } ref ModInt opAssign(T)(inout(T) a) if (is(T == uint) || is(T == ulong) || is(T == int) || is(T == long)) { return this = ModInt(a); } ref ModInt opOpAssign(string op, T)(T a) { static if (is(T == ModInt)) { static if (op == "+") { x = ((x += a.x) >= M) ? (x - M) : x; } else static if (op == "-") { x = ((x -= a.x) >= M) ? (x + M) : x; } else static if (op == "*") { x = cast(uint)((cast(ulong)(x) * a.x) % M); } else static if (op == "/") { this *= a.inv(); } else static assert(false); return this; } else static if (op == "^^") { if (a < 0) return this = inv()^^(-a); ModInt b = this, c = 1U; for (long e = a; e; e >>= 1) { if (e & 1) c *= b; b *= b; } return this = c; } else { return mixin("this " ~ op ~ "= ModInt(a)"); } } ModInt inv() const { uint a = M, b = x; int y = 0, z = 1; for (; b; ) { const q = a / b; const c = a - q * b; a = b; b = c; const w = y - cast(int)(q) * z; y = z; z = w; } assert(a == 1); return ModInt(y); } ModInt opUnary(string op)() const { static if (op == "+") { return this; } else static if (op == "-") { ModInt a; a.x = x ? (M - x) : 0U; return a; } else static assert(false); } ModInt opBinary(string op, T)(T a) const { return mixin("ModInt(this) " ~ op ~ "= a"); } ModInt opBinaryRight(string op, T)(T a) const { return mixin("ModInt(a) " ~ op ~ "= this"); } bool opCast(T: bool)() const { return (x != 0U); } string toString() const { return x.to!string; } } enum MO = 998244353; alias Mint = ModInt!MO; enum LIM_INV = 2 * 10^^6 + 10; Mint[] inv, fac, invFac; void prepare() { inv = new Mint[LIM_INV]; fac = new Mint[LIM_INV]; invFac = new Mint[LIM_INV]; inv[1] = 1; foreach (i; 2 .. LIM_INV) { inv[i] = -((Mint.M / i) * inv[cast(size_t)(Mint.M % i)]); } fac[0] = invFac[0] = 1; foreach (i; 1 .. LIM_INV) { fac[i] = fac[i - 1] * i; invFac[i] = invFac[i - 1] * inv[i]; } } Mint binom(long n, long k) { if (n < 0) { if (k >= 0) { return (-1)^^(k & 1) * binom(-n + k - 1, k); } else if (n - k >= 0) { return (-1)^^((n - k) & 1) * binom(-k - 1, n - k); } else { return Mint(0); } } else { if (0 <= k && k <= n) { assert(n < LIM_INV); return fac[cast(size_t)(n)] * invFac[cast(size_t)(k)] * invFac[cast(size_t)(n - k)]; } else { return Mint(0); } } } /* EC section 7.17 (# of border-strip tableaux of shape A and type (2,...,2)) = (-1)^* \chi^A(2,...,2) = (-1)^* [x^(A+\delta)] p[2]^* a[A+\delta] p[2] = x[0]^2 + ... + x[M-1]^2 split (A+\delta) into even and odd (-1)^* binom(*,*) ([x^(even/2)] p[1]^* a[\delta]) ([x^((odd-1)/2)] p[1]^* a[\delta]) = (-1)^* binom(*,*) (# of SYT) (# of SYT) */ Mint solve(int[] bs) { const bsLen = cast(int)(bs.length); auto cs = new int[bs[0]]; foreach (y; 0 .. bs[0]) { cs[y] = cast(int)(bs.count!(b => (b > y))); } Mint ret = 1; foreach (x; 0 .. bsLen) foreach (y; 0 .. bs[x]) { ret *= inv[(bs[x] - x) + (cs[y] - y) - 1]; } return ret; } void main() { prepare; try { for (; ; ) { const M = readInt; auto A = new int[M]; foreach (i; 0 .. M) { A[i] = readInt; } A.reverse; int[][2] bss; foreach (i; 0 .. M) { const ad = A[i] + (M - 1 - i); bss[ad & 1] ~= ad / 2; } foreach (h; 0 .. 2) { const bsLen = cast(int)(bss[h].length); foreach (i; 0 .. bsLen) { bss[h][i] -= (bsLen - 1 - i); } } debug { writeln("bss = ", bss); } Mint ans; if (bss[0].length == M - M / 2 && bss[1].length == M / 2 && bss[0].all!"a >= 0" && bss[1].all!"a >= 0") { ans = fac[A.sum / 2]; ans *= solve(bss[0]); ans *= solve(bss[1]); } writeln(ans); } } catch (EOFException e) { } }