fun main() {
    val builder = StringBuilder()

    val t = readInputLine().toInt()

    repeat(t) {
        var ok = true
        var gCnt = 0
        var lastWhite = false
        readInputLine().forEach {
            when(it) {
                'G' -> {
                    gCnt++
                    lastWhite = false
                }
                'R' -> {
                    if (gCnt <= 0) {
                        ok = false
                    } else {
                        gCnt--
                    }
                    lastWhite = false
                }
                else -> lastWhite = true
            }
        }
        builder.appendln(if (ok && !lastWhite && gCnt == 0) "possible" else "impossible")
    }

    print(builder.toString())
}

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