FERMATS LITTLE THEOREM

import java.math.*;
import java.io.*;
import java.util.Scanner;
public class Main
{
public static void main(String[] args) {
   Scanner s = new Scanner(System.in);
    System.out.println("Enter a prime number");
    BigInteger a=new BigInteger(s.next());
    System.out.println("Enter a number which is co prime of above number");
    BigInteger b=new BigInteger(s.next());
    if((a.gcd(b)).intValue()==1){
        System.out.println(b.modPow(BigInteger.valueOf(a.intValue()-2),a));
        
    }
    else{
        System.out.println("Invalid input");
    }

}
}