import std.algorithm, std.array, std.container, std.range;
import std.numeric, std.math, std.bigint, std.bitmanip, std.random;
import std.string, std.conv, std.stdio, std.typecons;

void main()
{
  auto t = readln.chomp.to!int;

  foreach (_; 0..t)
    writeln(calc(readln.chomp) ? "possible" : "impossible");
}

bool calc(string s)
{
  auto a = 0, b = 0, c = false, d = 0;

  foreach_reverse (t; s) {
    switch (t) {
    case 'R':
      a += 1;
      break;
    case 'G':
      b += 1;
      c = true;
      d -= 1;
      if (a < b) return false;
      break;
    case 'W':
      if (!c) return false;
      else if (d < 0) d += 1;
      break;
    default: assert(0);
    }
  }

  return (a == b && d == 0);
}