Find Duplicate in Range 0 and n-1

#include <stdio.h>

int find_duplicate(int arr[], int n) {
    // Your logic here
    int check;
    int count=0;
    for(int i=0 ;i < n ;i++){
        check = arr[i];
        for(int j = 0; j< n;j++){
            if(check == arr[j]){
                count++;
            }
        }
    }
    if(count >=2){
            return check;
        }
    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;
}