Find Duplicate in Range 0 and n-1

#include <stdio.h>
#include <math.h>


int max_element(int arr[], int n)
{
    if(n == 1)
    {
        return arr[0];
    }
    int maxVal = arr[0];
    for(int i=1; i<n; i++)
    {
        if(arr[i] > maxVal)
        {
            maxVal = arr[i];
        }
    }
    return maxVal;
}

int sum_array(int arr[], int n)
{
    int sum = 0;
    for(int i=0; i<n; i++)
    {
        sum+=arr[i];
    }
    return sum;
}


int find_duplicate(int arr[], int n) {
    // Your logic here
    int maxVal = max_element(arr, n);
    int arraySum = sum_array(arr, n);
    return arraySum - ((maxVal) * (maxVal + 1))/2;
}

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;
}