foo.cc: In function 'void tarjan(int)':
foo.cc:21:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   21 | for (int i = 0; i < e[u].size(); ++i) {
      |                 ~~^~~~~~~~~~~~~
foo.cc: In function 'void upd()':
foo.cc:47:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   47 | for (int j = 0; j < e[i].size(); ++j) {
      |                 ~~^~~~~~~~~~~~~
foo.cc: In function 'void dfs(int)':
foo.cc:56:19: warning: comparison of integer expressions of different signedness: 'int' and 'std::vector<int>::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   56 | for (int i = 0; i < e[u].size(); ++i) {
      |                 ~~^~~~~~~~~~~~~
foo.cc: In function 'int main()':
foo.cc:65:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   65 | scanf("%d%d", &n, &m);
      | ~~~~~^~~~~~~~~~~~~~~~
foo.cc:66:35: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   66 | for (int i = 1; i <= n; ++i) scanf("%d", w + i);
      |                              ~~~~~^~~~~~~~~~~~~
foo.cc:69:6: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   69 | scanf("%d%d", &u, &v);
      | ~~~~~^~~~~~~~~~~~~~~~

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