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)); } bool solve(const(long[]) A) { const N = cast(int)(A.length); auto bs = new long[N]; bs[0] = A[0]; foreach (i; 1 .. N) { bs[i] = A[i] - bs[i - 1]; } foreach (i; 0 .. N) { if (bs[i] < 0) { return false; } } if (bs[N - 1] != 0) { return false; } auto can = new bool[N - 1]; foreach (i; 0 .. N - 1) if (bs[i] > 0) { can[i] = ((A[i] & 1) == (A[i + 1] & 1)); } foreach (i; 1 .. N - 1) if (bs[i] > 0) { if (can[i - 1]) can[i] = true; } foreach_reverse (i; 0 .. N - 1 - 1) if (bs[i] > 0) { if (can[i + 1]) can[i] = true; } foreach (i; 0 .. N) if (bs[i] > 0) { if (!can[i]) { return false; } } int[] cuts; cuts ~= 0; foreach (i; 0 .. N - 1) if (bs[i] == 0) { cuts ~= i + 1; } const len = cast(int)(cuts.length); cuts ~= N; auto cnt = new int[2][N + 1]; foreach (i; 0 .. N) { cnt[i + 1] = cnt[i]; if (A[i] & 1) { ++cnt[i + 1][i & 1]; } } foreach (j; 0 .. len) { const i0 = cuts[j]; const i1 = cuts[j + 1]; if (cnt[i1][0] - cnt[i0][0] != cnt[i1][1] - cnt[i0][1]) { return false; } /* if (i1 - i0 >= 2) { bool ok; foreach (i; i0 .. i1 - 1) if ((A[i] & 1) == (A[i + 1] & 1)) { ok = ok || (bs[i] >= 2); ok = ok || (bs[i] == 1 && cnt[i][0] - cnt[i0][0] + (!(i & 1) && !(A[i] & 1)) == cnt[i][1] - cnt[i0][1] + ((i & 1) && !(A[i] & 1))); } if (!ok) { return false; } } */ } foreach (i; 0 .. N - 1) { if (bs[i] < abs(cnt[i + 1][1] - cnt[i + 1][0])) { return false; } } return true; } void main() { debug {{ enum N = 10; enum A = 6; auto dp = new bool[A^^N]; dp[0] = true; foreach (p; 0 .. A^^N) if (dp[p]) { const as = iota(N).map!(i => p / A^^i % A).array; foreach (i; 0 .. N - 1) { if (as[i] + 1 < A && as[i + 1] + 1 < A && (as[i] & 1) == (as[i + 1] & 1)) { dp[p + A^^i + A^^(i + 1)] = true; } } } foreach (p; 0 .. A^^N) { const as = iota(N).map!(i => cast(long)(p / A^^i % A)).array; const res = solve(as); assert(dp[p] == res, format("%s: %s %s", as, dp[p], res)); } }} try { for (; ; ) { const N = readInt; auto A = new long[N]; foreach (i; 0 .. N) { A[i] = readInt; } const ans = solve(A); writeln(ans ? "Yes" : "No"); } } catch (EOFException e) { } }