#include <bits/stdc++.h>   using namespace std;   const int INF = 1e9 + 10;   const int MN = 1e5 + 10;   int n, a[MN << 1], b[MN << 1];   struct cmp {     bool operator()(const int &x, const int &y) {       if (a[x] + b[x] != a[y] + b[y]) return a[x] + b[x] > a[y] + b[y];       return x > y;     }   };   set<int, cmp> S;   int main() {     ios_base ::sync_with_stdio(false), cin.tie(0), cout.tie(0);     cin >> n;     long long ans = 0;     for (int i = 0; i < n; ++i) {       cin >> a[2 * i] >> b[2 * i] >> a[2 * i + 1] >> b[2 * i + 1];       int x = a[2 * i] + b[2 * i], y = a[2 * i + 1] + b[2 * i + 1];       if (a[2 * i] > b[2 * i + 1] || b[2 * i] > a[2 * i + 1]) {         if (x >= y)           S.insert(2 * i), S.insert(2 * i + 1);         else {           if (a[2 * i] > b[2 * i + 1])             ans += a[2 * i] - b[2 * i + 1];           else             ans += a[2 * i + 1] - b[2 * i];         }       }     }     bool turn = false;     while (!S.empty()) {       int x = *S.begin();       S.erase(S.begin());       if (!turn)         ans += a[x];       else         ans -= b[x];       turn = !turn;     }     cout << ans <<   n ;     return 0;   }   