answer.code: In function ‘bool bfs(int)’:
answer.code:16:16: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   16 |     for (auto &[v, i] : adj[u]) {
      |                ^
answer.code: In function ‘int dfs(int, int, int)’:
answer.code:28:14: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   28 |   for (auto &[v, i] : adj[u]) {
      |              ^
answer.code: In function ‘int sol()’:
answer.code:61:11: error: ‘xs’ was not declared in this scope
   61 |   int N = xs.size() + ys.size();
      |           ^~
answer.code:61:23: error: ‘ys’ was not declared in this scope; did you mean ‘yn’?
   61 |   int N = xs.size() + ys.size();
      |                       ^~
      |                       yn
answer.code:83:14: warning: structured bindings only available with ‘-std=c++17’ or ‘-std=gnu++17’
   83 |   for (auto &[x, y] : ans) cout << 1 + x << " " << 1 + y << "\n";
      |              ^
answer.code: In function ‘int main()’:
answer.code:92:14: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   92 |       freopen((taskname"." + iext).c_str(), "r", stdin);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
answer.code:93:14: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   93 |       freopen(taskname".out", "w", stdout);
      |       ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~