fun main() {
    val builder = StringBuilder()

    val t = readInputLine().toInt()

    repeat(t) {
        val input = readInputLine()
        var ok = true
        var rCnt = 0
        var gCnt = 0
        var wCnt = 0

        input.forEach {
            when(it) {
                'G' -> {
                    gCnt++
                    if (gCnt > wCnt) {
                        ok = false
                    }
                }
                'R' -> {
                    rCnt++
                    if (rCnt > wCnt || rCnt > gCnt) {
                        ok = false
                    }
                }
                else -> {
                    wCnt++
                }
            }
        }

        gCnt = 0
        rCnt = 0
        wCnt = 0

        input.reversed().forEach {
            when(it) {
                'G' -> {
                    gCnt++
                    if (gCnt > rCnt) {
                        ok = false
                    }
                }
                'R' -> {
                    rCnt++
                }
                else -> {
                    wCnt++
                    if (gCnt == 0 || wCnt == 0) {
                        ok = false
                    }
                }
            }
        }
        builder.appendln(if (ok) "possible" else "impossible")
    }

    print(builder.toString())
}

fun readInputLine(): String {
    return readLine()!!
}