题解

#include<bits/stdc++.h>
using namespace std;
int a,b,dp[105][105];
int main(){
	cin>>a>>b;
    dp[1][0]=1;
	for(int j=1;j<=b;j++){
		for(int i=1;i<=a;i++){
            if(i-1<=0)dp[i][j]=dp[a][j-1]+dp[i+1][j-1];
            else if(i+1>a)dp[i][j]=dp[i-1][j-1]+dp[1][j-1];
			else dp[i][j]=dp[i-1][j-1]+dp[i+1][j-1];
		}
	}
	cout<<dp[1][b];
	return 0;
}