高精度快速幂（Java版）

 import java.io.*;
 import java.math.*;
 import java.util.*;
 import java.text.*;
 
 public class Main {
     public static void main(String[] args) {
         Scanner cin = new Scanner(System.in);
         BigInteger a, b, m, ans;
         while (cin.hasNext()) {
             ans = new BigInteger("1");
             a = cin.nextBigInteger();
             b = cin.nextBigInteger();
             m = cin.nextBigInteger();
             a = a.mod(m);
             while (b.compareTo(new BigInteger("0")) > 0) {
                 if (b.mod(BigInteger.valueOf(2)).compareTo(BigInteger.ONE) == 0) // if(n%2==1)
                     ans = ans.multiply(a).mod(m); // sq=(sq*p)%m;
                 a = a.multiply(a).mod(m); // p=(p*p)%m;
                 b = b.divide(BigInteger.valueOf(2));
             }
             System.out.println(ans);
         }
     }
 }