#백준_1331 나이트 투어 - Java 자바

# 유형 : 시뮬레이션

# 같은 곳 두번 가는 예외처리를 생각해주면 바로 풀 수 있던 문제.

# 난이도 : 실버 V

package bj;
 
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
 
public class p1331 {
    static int moveX[] = {1,2,2,1,-1,-2,-2,-1};
    static int moveY[] = {2,1,-1,-2,-2,-1,1,2};
    static String str[];
    static boolean visit[][];
    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        str = new String[37];
        for(int i=0; i<36; i++) {
            str[i] = br.readLine();
        }
        str[36] = str[0];
        int index=0;
        visit = new boolean[6][6];
        boolean check = true;
        while(index<36) {
            String current = str[index];
            String next = str[index+1];
            
            char current_x = current.charAt(0);
            char current_y = current.charAt(1);
            
            visit[current_y -'0'-1][current_x - 'A'] = true;
            
            char next_x = next.charAt(0);
            char next_y = next.charAt(1);
            
            int diff_x = Math.abs(current_x - next_x);
            int diff_y = Math.abs(current_y - next_y);
            boolean isTrue = false;
            for(int d=0; d<8; d++) {
                if(moveX[d] == diff_x && moveY[d] == diff_y) {
                    isTrue = true;
                    break;
                }
            }
            if(!isTrue) {
                check = false;
                System.out.println("Invalid");
                return;
            }
            if(visit[next_y-'0'-1][next_x-'A']) {
                if(index!=35) {
                    check = false;
                    System.out.println("Invalid");
                    return;
                }
            }
            
            index++;
        }
        if(check)
            System.out.println("Valid");
    }
}