Missing Number in java with example

import java.io.*;
import java.util.*;
class Missno
{
public static void main(String arg[])
{
Scanner obj=new Scanner(System.in);
System.out.println("enter n value");
int n=obj.nextInt();
int sum=0;
int c,i,a[]=new int[n];;
System.out.println("enter values");
for(i=0;i<n-1;i++)
{
a[i]=obj.nextInt();
sum=sum+a[i];
}
c=(n*(n+1)/2)-sum;
System.out.println("missing no is: "+c);
}
}

Output:
PS C:\Users\Pramod> & 'c:\Users\Pramod\.vscode\extensions\vscjava.vscode-java-debug-0.31.0\scripts\launcher.bat' 'C:\Program Files\Java\jdk-15.0.2\bin\java.exe' '--enable-preview' '-XX:+ShowCodeDetailsInExceptionMessages' '-Dfile.encoding=UTF-8' '-cp' 'C:\Users\Pramod\AppData\Local\Temp\vscodesws_624b1\jdt_ws\jdt.ls-java-project\bin' 'Missno'
enter n value
5
enter values
1
2
4
5
missing no is: 3
PS C:\Users\Pramod>