Find Duplicate in Range 0 and n-1

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    // Your logic here
    int left = 0;
    int right = n - 1;
    int sub = arr[left];
    while(left <= right){
        while(left <= right){
            if(arr[left] == arr[right]){
                sub = arr[left];
                return sub;
            }
            left++;
        }
        right--;
        left = 0;
    }
    return -1;
}

int main() {
    int n;
    scanf("%d", &n);

    int arr[100];
    for (int i = 0; i < n; i++) scanf("%d", &arr[i]);

    int result = find_duplicate(arr, n);
    printf("%d", result);
    return 0;
}