Problem p03062 (C++)

Buggy submission (status: Runtime Error):
#include <algorithm>
#include <bitset>
#include <cmath>
#include <deque>
#include <functional>
#include <iostream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define a first
#define b second
#define sz(x) (ll)((x).size())
#define pb push_back
#define mp make_pair
#define bg begin()
#define ed end()
#define all(x) (x).bg, (x).ed
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rep1(i, n) for (ll i = 1; i <= (n); i++)
#define rrep(i, n) for (ll i = (n)-1; i >= 0; i--)
#define rrep1(i, n) for (ll i = (n); i >= 1; i--)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
const ll MOD = 1000000007;
const ll INF = 1000000000000000;
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
ll maxx(ll x, ll y, ll z) { return max(max(x, y), z); }
ll minn(ll x, ll y, ll z) { return min(min(x, y), z); }
ll gcd(ll x, ll y) {
  if (x % y == 0)
    return y;
  else
    return gcd(y, x % y);
}
ll lcm(ll x, ll y) { return x * (y / gcd(x, y)); }
ll digsz(ll x) {
  if (x == 0)
    return 1;
  else {
    ll ans = 0;
    while (x) {
      x /= 10;
      ans++;
    }
    return ans;
  }
}
ll digsum(ll x) {
  ll sum = 0;
  while (x) {
    sum += x % 10;
    x /= 10;
  }
  return sum;
}
vector<ll> pw2(62, 1);
vector<ll> pw10(19, 1);

int main() {
  { rep1(i, 61) pw2[i] = 2 * pw2[i - 1]; }
  { rep1(i, 18) pw10[i] = 10 * pw10[i - 1]; }

  ll N;
  cin >> N;
  ll ans = 0;
  vector<ll> minus;
  vector<ll> plus;
  rep(i, N) {
    ll tmp;
    cin >> tmp;
    if (tmp < 0)
      minus.pb(tmp);
    else
      plus.pb(tmp);
  }
  sort(all(plus));
  sort(all(minus));
  if (sz(minus) % 2 == 0) {
    rep(i, sz(minus)) { ans -= minus[i]; }
    rep(i, sz(plus)) { ans += plus[i]; }
  } else {
    rep(i, sz(minus) - 1) { ans -= minus[i]; }
    rep1(i, sz(plus) - 1) { ans += plus[i]; }
    ans += abs(abs(minus[sz(minus) - 1]) - abs(plus[0]));
  }
  cout << ans << endl;
}


Fixed submission:
#include <algorithm>
#include <bitset>
#include <cmath>
#include <deque>
#include <functional>
#include <iostream>
#include <iterator>
#include <map>
#include <queue>
#include <set>
#include <stack>
#include <string>
#include <utility>
#include <vector>
using namespace std;
typedef long long ll;
typedef pair<ll, ll> P;
#define a first
#define b second
#define sz(x) (ll)((x).size())
#define pb push_back
#define mp make_pair
#define bg begin()
#define ed end()
#define all(x) (x).bg, (x).ed
#define rep(i, n) for (ll i = 0; i < (n); i++)
#define rep1(i, n) for (ll i = 1; i <= (n); i++)
#define rrep(i, n) for (ll i = (n)-1; i >= 0; i--)
#define rrep1(i, n) for (ll i = (n); i >= 1; i--)
#define FOR(i, a, b) for (ll i = (a); i < (b); i++)
const ll MOD = 1000000007;
const ll INF = 1000000000000000;
template <class T> inline bool chmin(T &a, T b) {
  if (a > b) {
    a = b;
    return true;
  }
  return false;
}
template <class T> inline bool chmax(T &a, T b) {
  if (a < b) {
    a = b;
    return true;
  }
  return false;
}
ll maxx(ll x, ll y, ll z) { return max(max(x, y), z); }
ll minn(ll x, ll y, ll z) { return min(min(x, y), z); }
ll gcd(ll x, ll y) {
  if (x % y == 0)
    return y;
  else
    return gcd(y, x % y);
}
ll lcm(ll x, ll y) { return x * (y / gcd(x, y)); }
ll digsz(ll x) {
  if (x == 0)
    return 1;
  else {
    ll ans = 0;
    while (x) {
      x /= 10;
      ans++;
    }
    return ans;
  }
}
ll digsum(ll x) {
  ll sum = 0;
  while (x) {
    sum += x % 10;
    x /= 10;
  }
  return sum;
}
vector<ll> pw2(62, 1);
vector<ll> pw10(19, 1);

int main() {
  { rep1(i, 61) pw2[i] = 2 * pw2[i - 1]; }
  { rep1(i, 18) pw10[i] = 10 * pw10[i - 1]; }

  ll N;
  cin >> N;
  ll ans = 0;
  vector<ll> minus;
  vector<ll> plus;
  rep(i, N) {
    ll tmp;
    cin >> tmp;
    if (tmp < 0)
      minus.pb(tmp);
    else
      plus.pb(tmp);
  }
  sort(all(plus));
  sort(all(minus));
  if (sz(minus) % 2 == 0) {
    rep(i, sz(minus)) { ans -= minus[i]; }
    rep(i, sz(plus)) { ans += plus[i]; }
  } else {
    rep(i, sz(minus) - 1) { ans -= minus[i]; }
    rep1(i, sz(plus) - 1) { ans += plus[i]; }
    if (sz(plus) > 0)
      ans += abs(abs(minus[sz(minus) - 1]) - abs(plus[0]));
    else
      ans += minus[sz(minus) - 1];
  }
  cout << ans << endl;
}