import core.thread; import std.conv, std.stdio, std.string; import std.algorithm, std.array, std.bigint, std.container, std.math, std.range, std.regex; // Input 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[0]; tokens.popFront; return token; } int readInt() { return to!int(readToken); } long readLong() { return to!long(readToken); } real readReal() { return to!real(readToken); } // chmin/chmax void chmin(T)(ref T t, in T f) { if (t > f) t = f; } void chmax(T)(ref T t, in T f) { if (t < f) t = f; } // Pair struct Pair(S, T) { S x; T y; int opCmp( const Pair p) const { return (x < p.x) ? -1 : (x > p.x) ? +1 : (y < p.y) ? -1 : (y > p.y) ? +1 : 0; } int opCmp(ref const Pair p) const { return (x < p.x) ? -1 : (x > p.x) ? +1 : (y < p.y) ? -1 : (y > p.y) ? +1 : 0; } string toString() const { return "(" ~ to!string(x) ~ ", " ~ to!string(y) ~ ")"; } } auto pair(S, T)(inout(S) x, inout(T) y) { return Pair!(S, T)(x, y); } // Array int binarySearch(T)(in T[] as, in bool delegate(T) test) { int low = -1, upp = as.length; for (; low + 1 < upp; ) { int mid = (low + upp) >> 1; (test(as[mid]) ? low : upp) = mid; } return upp; } int lowerBound(T)(in T[] as, in T val) { return as.binarySearch((T a) { return (a < val); }); } int upperBound(T)(in T[] as, in T val) { return as.binarySearch((T a) { return (a <= val); }); } T[] unique(T)(in T[] as) { T[] bs; foreach (a; as) if (bs.empty || bs[$ - 1] != a) bs ~= a; return bs; } void prepare() { } class Solver : core.thread.Thread { size_t caseId; this(size_t caseId) { this.caseId = caseId; super(&main); } void main() { try { run; stderr.writeln("DONE Case #", caseId); } catch (Throwable e) { stderr.writeln("ERROR Case #", caseId, ": ", e.msg); } finally { stderr.flush; } } string S; bool ans; bool solve() { const int N = cast(int)(S.count('R')); int a = N, b = 0, c = 0, d = 0; foreach_reverse (s; S) { switch (s) { case 'R': { if (a == 0) { return false; } --a; ++b; } break; case 'G': { if (b == 0) { return false; } --b; ++c; } break; case 'W': { if (c + d == 0) { return false; } --c; ++d; } break; default: assert(false); } } return (a == 0 && b == 0 && c == 0 && d == N); } void run() { ans = solve; } void input() { S = readToken; } void output() { writeln(ans ? "possible" : "impossible"); stdout.flush; } } void main(string[] args) { bool parallel = false; foreach (arg; args) if (arg == "-p") parallel = true; prepare; auto solvers = new Solver[readInt]; foreach (caseId, ref solver; solvers) solver = new Solver(caseId + 1); if (parallel) { foreach (solver; solvers) solver.input, solver.start; foreach (solver; solvers) solver.join, solver.output; } else { foreach (caseId, solver; solvers) { solver.input; solver.run; solver.output; stderr.writeln("DONE Case #", caseId + 1); stderr.flush; } } }