#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int n,m,ans;
void f(int last,int step)
{
	if(last/2+1<step)
		return;
	if( 0 == step)
	{
		ans++;
		return ;
	}
	for(int i =last;i >=1;i--)
		f(i-2,step - 1);
}
int main()
{
	cin >> n >> m;
	f(n,m);
	cout<< ans<<endl;
	return 0;
}

/*****************************************
备注：
******************************************/
#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int n,m,ans;
void f(int last,int step)
{
	if(last/2+1<step)
		return;
	if(0==step)
	{
		ans++;
		return;
	}
	for(int i=last;i>=1;i--)
		f(i-2,step-1);
}
int main()
{
	cin>>n>>m;
	f(n,m);
	cout<<ans<<endl;
	return 0;
}

C++

#include <iostream>
#include <stdio.h>
#include <string.h>
#include <queue>
#include <math.h>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <stack>

using namespace std;

#define LL long long
const int N =1e5+10;
const int INF =0x3f3f3f3f;
int n,m,ans;
void f(int last ,int step){
	if(last/2+1<step)
		return;
	if(0== step){
		ans++;
		return;
	}
	for(int i=last;i>=1;i--)
		f(i-2,step-1);
}
int main(){
	cin>>n>>m;
	f(n,m);
	cout<<ans<<endl; 
	return 0;
}

C++
#include <iostream>
#include <stdio.h>
#include <string.h>
#include <queue>
#include <math.h>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <stack>

using namespace std;

#define LL long long
const int N =1e5+10;
const int INF =0x3f3f3f3f;
int n,m,ans;
void f(int last ,int step){
	if(last/2+1<step)
		return;
	if(0== step){
		ans++;
		return;
	}
	for(int i=last;i>=1;i--)
		f(i-2,step-1);
}
int main(){
	cin>>n>>m;
	f(n,m);
	cout<<ans<<endl; 
	return 0;
}

/*****************************************
备注：
******************************************/
#include <queue>
#include <math.h>
#include <stack>
#include <stdio.h>
#include <iostream>
#include <vector>
#include <iomanip>
#include <string.h>
#include <algorithm>
using namespace std;
#define LL long long
const int N = 1e5 + 10;
const int INF = 0x3f3f3f3f;
int n,m,ans;
void f(int last,int step)
{
	if(last/2+1<step)
		return;
	if(0==step)
	{
		ans++;
		return;
	}
	for(int i=last;i>=1;i--)
		f(i-2,step-1);
}
int main()
{
	cin>>n>>m;
	f(n,m);
	cout<<ans<<endl;
	return 0;
}