Valid 4x4 Grid Checker

You are given a 4x4 grid. Your task is to check whether the grid contains every integer from \(1\) to \(16\) exactly once. In other words, the grid must contain the set \(\{1,2,\dots,16\}\) with no duplicates and no missing numbers.

Read the input from standard input (stdin) and print the result to standard output (stdout). If the grid is valid, output VALID; otherwise, output INVALID.

inputFormat

The input consists of 4 lines. Each line contains 4 space-separated integers representing a row of the grid.

outputFormat

Output a single line containing either 'VALID' or 'INVALID' based on whether the grid is valid.## sample

1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16

VALID