Can anyone reduce the complexity of my code. Problem E of codeforces round113 div.2

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algorithm

DSA

optimization

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Link to The Problem: https://codeforces.com/problemset/problem/166/E[^]

Problem Statement:

*You are given a tetrahedron. Let's mark its vertices with letters A, B, C, and D correspondingly.

An ant is standing in the vertex D of the tetrahedron. The ant is quite active and he wouldn't stay idle. At each moment of time, he makes a step from one vertex to another one along some edge of the tetrahedron. The ant just can't stand on one place. You do not have to do much to solve the problem: your task is to count the number of ways in which the ant can go from the initial vertex D to itself in exactly n steps. In other words, you are asked to find out the number of different cyclic paths with the length of n from vertex D to itself. As the number can be quite large, you should print it modulo 1000000007 (10e9 + 7).*

Input: The first line contains the only integer n (1 ≤ n ≤ 107) — the required length of the cyclic path.

Output: Print the only integer — the required number of ways modulo 1000000007 (10e9 + 7).

Example: Input n=2 , Output: 3 Input n=4, Output: 21

What I have tried:

My Approach to Problem: I have written a recursive code that takes two input n and present index, then I am traveling and exploring all possible combinations.

#include<iostream>
using namespace std;
#define ll long long 
#define mod 10000000  
ll count_moves=0;
    ll count(ll n, int present)
    {   
        if(n==0 and present==0) count_moves+=1, count_moves%=mod;  //base_condition
        else if(n>1){                   //Generating All possible Combinations 
            count(n-1,(present+1)%4);
            count(n-1,(present+2)%4);
            count(n-1,(present+3)%4);
        }
        else if(n==1 and present) count(n-1,0);
    }
    int main()
    {
        ll n;  cin>>n;
        if(n==1) {  cout<<"0";  return;   } 
        count(n,0);
        cout<<count_moves%mod;
    }

But the problem is that I am getting Time Limit Error since Time Complexity of my Code is very high. Please Can anyone suggest me how can I optimize/Memoize my code to reduce its complexity?