func_code_string: #include <bits/stdc++.h>   using namespace std;   int a[1005];   int b[2005];   int main() {     int p, q, l, r;     cin >> p >> q >> l >> r;     while (p--) {       int val1, val2;       cin >> val1 >> val2;       for (int i = val1; i <= val2; i++) a[i] = 1;     }     while (q--) {       int val1, val2;       cin >> val1 >> val2;       for (int i = val1; i <= val2; i++) b[i + 1000] = 1;     }     int count = 0;     for (int t = l; t <= r; t++)       for (int i = 0; i <= 1000; i++)         if (a[i] && b[i + 1000 - t]) {           count++;           break;         }     cout << count;     return 0;   }   