Problem p03062 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop                                                                   \
  char nyaa;                                                                   \
  cin >> nyaa;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;

int n;
ll S = 0;
vector<ll> a, pos, neg;

void solve() {
  cin >> n;
  a.resize(n, 0);
  rep(i, n) {
    cin >> a[i];
    if (a[i] >= 0)
      pos.push_back(a[i]);
    else
      neg.push_back(a[i]);
  }
  rep(i, n) {
    if (a[i] >= 0)
      S += a[i];
    else
      S -= a[i];
  }
  if (neg.size() % 2 == 0) {
    cout << S << endl;
  } else {
    sort(neg.begin(), neg.end());
    sort(pos.begin(), pos.end());
    cout << S - 2 * min(pos[0], -neg.back()) << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
}

Fixed submission:
#include <algorithm>
#include <bitset>
#include <ciso646>
#include <cmath>
#include <complex>
#include <cstdio>
#include <functional>
#include <iomanip>
#include <iostream>
#include <map>
#include <queue>
#include <random>
#include <set>
#include <stack>
#include <string>
#include <tuple>
#include <unordered_map>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop                                                                   \
  char nyaa;                                                                   \
  cin >> nyaa;
#define rep(i, n) for (int i = 0; i < n; i++)
#define per(i, n) for (int i = n - 1; i >= 0; i--)
#define Rep(i, sta, n) for (int i = sta; i < n; i++)
#define rep1(i, n) for (int i = 1; i <= n; i++)
#define per1(i, n) for (int i = n; i >= 1; i--)
#define Rep1(i, sta, n) for (int i = sta; i <= n; i++)
typedef long double ld;
typedef complex<ld> Point;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;

int n;
ll S = 0;
vector<ll> a, pos = {INF}, neg;

void solve() {
  cin >> n;
  a.resize(n, 0);
  rep(i, n) {
    cin >> a[i];
    if (a[i] >= 0)
      pos.push_back(a[i]);
    else
      neg.push_back(a[i]);
  }
  rep(i, n) {
    if (a[i] >= 0)
      S += a[i];
    else
      S -= a[i];
  }
  if (neg.size() % 2 == 0) {
    cout << S << endl;
  } else {
    sort(neg.begin(), neg.end());
    sort(pos.begin(), pos.end());
    cout << S - 2 * min(pos[0], -neg.back()) << endl;
  }
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  solve();
}