Help Cupid Wrong Answer

#include <vector>
#include <list>
#include <map>
#include <set>
#include <queue>
#include <deque>
#include <stack>
#include <bitset>
#include <algorithm>
#include <functional>
#include <numeric>
#include <utility>
#include <sstream>
#include <iostream>
#include <iomanip>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <queue>
#include <ctime>
#include <cassert>
#include <climits>
#include <limits>
using namespace std;

typedef vector <int> vi;
typedef pair< int ,int > ii;

#define S(a) scanf("%d",&(a))
#define P(a) printf("%d",(a))
#define PS printf(" ")
#define NL printf("\n")
#define SL(a) scanf("%lld",&(a))
#define PL(a) printf("%lld",(a))
#define LL long long int
#define FOR(I,A,B) for(int I= (A); I<(B); ++I)
#define all(c) c.begin(), c.end()
#define stop system("pause")
#define pb push_back
#define mp make_pair
#define tr(container, it) for(typeof(container.begin()) it = container.begin(); it != container.end(); it++)
#define INDEX(arr,ind)          (lower_bound(all(arr),ind)-arr.begin())
#define ff first
#define ss second

#define imax numeric_limits<int>::max()
#define imin numeric_limits<int>::min()
#define lmax numeric_limits<ll>::max()
#define lmin numeric_limits<ll>::min()

int ar[1010];

struct node{
    int x;
    int y;
    int val;
};

vector<node> dist;

vector<node> store[25];

map<int,int> mark;

void init(){
    mark.clear();
    dist.clear();
    FOR(i,0,25)
        store[i].clear();

}

void do_sort(){                 //linear-time sorting
    int sz = dist.size();
    FOR(i,0,sz){
        store[dist[i].val].pb(dist[i]);
    }

    dist.clear();
    FOR(i,0,25){
        int sz = store[i].size();
        FOR(j,0,sz){
            dist.pb(store[i][j]);
        }
    }

}

int main(){
    int n;
    int flag = 0;
    while(S(n)==1){
        if(flag)
            NL;
        init();
        FOR(i,0,n){
            S(ar[i]);
            mark[ar[i]]++;      //mark stores the frequency of each element
        }
        FOR(i,0,n){
            FOR(j,i+1,n){
                int value =  min(abs(ar[i]-ar[j]),24-abs(ar[i]-ar[j]));
                node temp;
                temp.x = ar[i];
                temp.y = ar[j];
                temp.val = value;
                dist.pb(temp);
            }
        }

        do_sort();  //sort the distances
        int ct = 0;
        int ans = 0;
        int i = 0;

        while(ct<n/2){  //select N/2 distances

            if(mark[dist[i].x]==0 || mark[dist[i].y]==0 || (dist[i].x == dist[i].y && mark[dist[i].x]<=1) ){
                i++;
            }
            else{
                ans +=dist[i].val;
                mark[dist[i].x]--;
                mark[dist[i].y]--;
                ct++;
                i++;
            }
        }
        P(ans);
    }
    return 0;
}