import java.io.* ;
public class ttt {
    static int[] cross = new int[] {
	1, 1, 4, 1, 7, 1, 3, 3, 4, 3, 5, 3, 4, 4, 4, 2
    } ;
    public static void main(String[] args) throws Exception {
	BufferedReader br = new BufferedReader(new InputStreamReader(System.in)) ;
	while (true) {
	    String s = br.readLine() ;
	    if (s.startsWith("end"))
		return ;
	    int exes = 0 ;
	    int ohs = 0 ;
	    for (int i=0; i<9; i++)
		if (s.charAt(i) == 'X')
		    exes++ ;
		else if (s.charAt(i) == 'O')
		    ohs++ ;
	    boolean win[] = new boolean[128] ;
	    for (int i=0; i<cross.length; i+=2)
		if (s.charAt(cross[i]) == s.charAt(cross[i]+cross[i+1]) &&
		    s.charAt(cross[i]) == s.charAt(cross[i]-cross[i+1]))
		    win[s.charAt(cross[i])] = true ;
	    if ((exes == ohs && win['O'] && !win['X']) ||
		(exes == ohs + 1 && win['X'] && !win['O']) ||
		(exes == 5 && ohs == 4 && !win['X'] && !win['O']))
		System.out.println("valid") ;
	    else
		System.out.println("invalid") ;
	}
    }
}