func_code_string: #include <bits/stdc++.h>   using namespace std;   int const N = 1e6 + 6;   bool us[N], use[N];   long long a[N];   long long n, x, k, q, x1, x2, y, ibibibibbibibibiibigbabypanfewewf, y2, ans, m;   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     cin >> x1;     for (int I = 0; I < x1; I++) {       cin >> n;       y = 0;       ibibibibbibibibiibigbabypanfewewf = 1e9 + 7;       for (int i = 1; i <= n; i++) {         cin >> k >> q;         y = max(y, k);         ibibibibbibibibiibigbabypanfewewf =             min(ibibibibbibibibiibigbabypanfewewf, q);       }       cout << max(0ll, y - ibibibibbibibibiibigbabypanfewewf) << endl;     }   }   