Find Duplicate in Range 0 and n-1

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    // Your logic here
    //Double loop
    //Loop over every element & compare for double occurance
    int occurances=0;
    for(int i=0;i<n;i++){ //(0-n) Compare number 0-n
        occurances = 0; //Reset occurances
        for(int j=0;j<n;j++){ //(0-n)
            if(arr[j] == i){ //Check if array element matches 0-n
                occurances++; //If it matches, increase occurance
            }
            if(occurances > 1){ //Check if that occurance has appeared before
                return i; //Return the number that has reoccured
            }
        }
    }
    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;
}