#include<iostream>
#include<cstring>
using namespace std;
int range,random,way_count=0;
int number=0,num_list[1010];
int judge_number(int floor,int step){
	if(floor==random+1){
		if(number==range){
			way_count++;
		}
		return 0;
	}
	for(int i=step;i<=range;i++){
		num_list[floor]=i;
		number+=num_list[floor];
		judge_number(floor+1,i);
		number-=num_list[floor];
		num_list[floor]=0;
	}
}
int main(){
	cin>>range>>random;
	judge_number(1,1);
	cout<<way_count;
	return 0;
}

递归真的慢。看一看......