foo.cc: In function ‘void dfs(int)’:
foo.cc:73:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   73 |     for(int i=0;i<a1[x].size();i++) c1[a1[x][i]]++;
      |                 ~^~~~~~~~~~~~~
foo.cc:74:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   74 |     for(int i=0;i<b1[x].size();i++) c1[b1[x][i]]--;
      |                 ~^~~~~~~~~~~~~
foo.cc:75:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   75 |     for(int i=0;i<a2[x].size();i++) c2[a2[x][i]+n]++;
      |                 ~^~~~~~~~~~~~~
foo.cc:76:18: warning: comparison of integer expressions of different signedness: ‘int’ and ‘std::vector<int>::size_type’ {aka ‘long unsigned int’} [-Wsign-compare]
   76 |     for(int i=0;i<b2[x].size();i++) c2[b2[x][i]+n]--;
      |                 ~^~~~~~~~~~~~~