题目链接

题意:



题解:











就是分子

AC代码

/*
    Author:zzugzx
    Lang:C++
    Blog:blog.csdn.net/qq_43756519
*/
#include<bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define pb push_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define endl '\n'
#define SZ(x) (int)x.size()
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double,double> pdd;
const int mod=1e9+7;
//const int mod=998244353;
const double eps = 1e-10;
const double pi=acos(-1.0);
const int maxn=1e6+10;
const ll inf=0x3f3f3f3f;
const int dir[8][2]={{0,1},{1,0},{0,-1},{-1,0},{1,1},{1,-1},{-1,1},{-1,-1}};

ll dp[50][200];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(0);cout.tie(0);
    //freopen("in.txt","r",stdin);
    //freopen("out.txt","w",stdout);
    ll n;
    cin>>n;
    ll N=4*n;
    dp[0][0]=1;
    for(int i=1;i<=n;i++)
        for(int j=1;j<=4;j++)
            for(int k=N;k>=j;k--)
                dp[i][k]+=dp[i-1][k-j];
    ll ans=0;
    for(int i=3*n;i<=N;i++)ans+=dp[n][i];
    N=1ll<<(2*n);
    ll x=__gcd(ans,N);
    cout<<ans/x<<'/'<<N/x<<endl;
    return 0;
}