排列组合方法40分

#include <bits/stdc++.h>\
using namespace std;\
int A(int x,int y)\
{\
	int sum=1;\
	for(int i=x;i>=x-y+1;i--)\
		sum=sum*i;\
	return sum;\
}\
int C(int a,int b)\
{\
	return A(a,b)/A(b,b);\
}\

int main()\
{\
 	int a,b;\
 	cin>>a>>b;\
 	a=(a-1)/2;\
 	b=(b-1)/2;\
 	cout<<C(a+b,b);\
    return 0;\
}