#include <iostream>
#include <string>
using namespace std;

int main(void)
{
    int t;
    cin >> t;
    for(int i = 0; i < t; i++)
    {
        string str;
        int stack = 0;
        cin >> str;
        int size = str.size();
        if(size < 3 || str[size - 1] == 'W')
        {
            cout << "impossible" << endl;
            continue;
        }
        for(int j = 0; j < size; j++)
        {
            if(str[j] == 'G')
                stack++;
            else if(str[j] == 'R')
                stack--;
            if(stack < 0)
                break;
        }
        if(stack == 0)
            cout << "possible" << endl;
        else
            cout << "impossible" << endl;
    }
    return 0;
}