Find Missing Number (1 to N)

import java.util.*;
class Main{
public static void main(String[] args){
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();
int total=n*(n+1)/2;
int sum=0;
for(int num:arr) sum+=num;
System.out.println(total-sum);
}
}