Equilateral numbers

#include <bits/stdc++.h>

using namespace std;

int main()
{
    long long n;
    cin >> n;
    vector<short> save;
    long long cnt = 0;
    long long ser_cnt = 0;
    while(cnt < n+5){
        save.push_back(1);
        save.push_back(2);
        cnt+= 2;
        for(int i = 0; i < ser_cnt; i++){
            if(i %2 == 0){
                save.push_back(3);
            }else{
                save.push_back(2);
            }
            cnt++;
        }
        ser_cnt++;
    }
    /*
    for(int i = 0; i < n; i++){
        cout << save[i] << " ";
    }
    cout << endl;
    */
    cout << save[n-1];
}

Test 1

Verdict: ACCEPTED

Test 2

Verdict: ACCEPTED

Test 3

Verdict: ACCEPTED

Test 4

Verdict: ACCEPTED

Test 5

Verdict: WRONG ANSWER

Test 6

Verdict: RUNTIME ERROR

Test 7

Verdict: ACCEPTED

Test 8

Verdict: RUNTIME ERROR

Test 9

Verdict: RUNTIME ERROR

Test 10

Verdict: RUNTIME ERROR

Test 11

Verdict: RUNTIME ERROR

Test 12

Verdict: RUNTIME ERROR