физтех отбор 3

#include <iostream>
#include <cmath>
#include <vector>
#include <queue>
#include <algorithm>
#include <string>
#include <stack>
#include <set>
#include <map>
#define pii pair <int,int>
#define vec vector
using namespace std;
using ll = long long;
using ld = long double;
using db = double;
void cv(vector <int> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}

void cvl(vector <ll> &v){
    for (auto x: v) cout<<x<<' ';
    cout<<"\n";
}


void cvv(vector <vector <int> > &v){
    for (auto x: v) cv(x);
    cout<<"\n";
}

void cvb(vector <bool> v){
    for (bool x: v) cout<<x<<' ';
    cout<<"\n";
}

ll ans=0;

void dfs(int v, int cnt){
    //cout<<"v = "<<v<<'\n';
    //if (cnt <= 100) cout<<cnt<<"\n";
    if (cnt == 28 && v == 0) {
            //cout<<"one\n";
            ans++;
            return;
    }
    if (cnt == 28) return;
    //cout<<"two\n";
    for (int i = 0; i < 3 ; ++i){
        //cout<<"i = "<<i<<"\n";
        if (i == v) continue;
        dfs(i, cnt + 1);
    }
}

int main()
{
    /*ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);*/
	//cout.precision(1);
	dfs(0, 0);
	cout<<"ans = "<<ans<<"\n";
}