C++ :

#include<bits/stdc++.h>
using namespace std;
//根据题目意思，定义递归 
int Ack(int m,int n){
    if(m==0) return n+1;
    else if(m!=0 && n==0) return Ack(m-1,1);
    else return Ack(m-1,Ack(m,n-1));
}
int main(){
    int m,n;
    cin>>m>>n;
    cout<<Ack(m,n);
    return 0;
}

Java :

import java.util.Scanner;
public class Main{
public static void main (String[] args){
	Scanner sc = new Scanner(System.in);
	int m = sc.nextInt();
	int n = sc.nextInt();
	System.out.println(ack(m,n));
	
	
	
	}


public static int ack(int m ,int n) {
	int r;
	if(m == 0) {
		r = n + 1;
	}else if(n == 0) {
		r = ack(m - 1 ,1);
	}else {
		r = ack(m - 1,ack(m,n - 1));
	}
	
	return r;
}
 
}