Help me in solving DSAAGP07A problem

My issue

what is a hidden test case and why is it showing wrong ans even when my output matches the output provided

My code

#include <stdio.h>

int main() {
    int arr[100] = {4, 5, 3, 10, 12, 18}; // Initial array
    int size = 6;                 // Current size of the array

    int newPosition = 5; // Index where you want to insert the new element
    int newElement = 7; // Element to be inserted

    // Shift elements to make space for the new element
    for(int i = size; i >newPosition; i--){
        arr[i] = arr[i - 1];
    }




    // Insert the new element at the specified position
    arr[newPosition] = newElement;


    // Update the size of the array
    size++;

    // Print the updated array
    printf("Updated array: ");
    for(int i = 0; i < size; i++){
        printf("%d ", arr[i]);
    }




    return 0;
}

Learning course: Data structures & Algorithms lab
Problem Link: https://www.codechef.com/learn/course/muj-aiml-dsa-c/MUJADSAC05/problems/DSAAGP07A