The question quotes:
“Now Chef is asking you to count the number of ways to fill the missing numbers (ie. the -1s) of the array with level numbers, so that it corresponds to a valid game. Since the answer can be large, output it modulo 109+7.”
So, if there is no missing number the count is zero.
But the solutions getting accepted outputs answer 1.
Question link: https://www.codechef.com/COOK79/problems/COOKGAME