foo.cc: In function 'void spfa(long long int)':
foo.cc:24:35: warning: comparison of integer expressions of different signedness: 'long long int' and 'std::vector<std::pair<long long int, long long int> >::size_type' {aka 'long unsigned int'} [-Wsign-compare]
   24 |                 for (int i = 0; i < g[u].size(); i++) {
      |                                 ~~^~~~~~~~~~~~~

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