func_code_string: #include <bits/stdc++.h>   using namespace std;   int main() {     int n, i, l, r, l1 = 0, r1 = 1e9, l2 = 0, r2 = 1e9;     cin >> n;     for (i = 0; i < n; i++) {       cin >> l >> r;       l1 = max(l1, l);       r1 = min(r1, r);     }     cin >> n;     for (i = 0; i < n; i++) {       cin >> l >> r;       l2 = max(l2, l);       r2 = min(r2, r);     }     cout << max(l1 - r2, max(l2 - r1, 0));     return 0;   }   