Find missing number in array

DIPTOM

import java.util.Scanner;

public class Arraymissingnum {
public static void main(String args[]) {
int sum=0;
Scanner sc = new Scanner(System.in);
int n = sc.nextInt();
int[] arr = new int[n-1];
for (int i = 0; i < n-1; i++) {
arr[i] = sc.nextInt();
sum+=arr[i];
}
int s=n*(n+1)/2;

System.out.println(s-sum);
}
}