/in/foo.cc: In function 'MST merge(MST, MST, int*)':
/in/foo.cc:54:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.G.size();i++)G.push_back(a.G[i]);
              ~^~~~~~~~~~~
/in/foo.cc:55:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<b.G.size();i++)G.push_back((edge){b.G[i].u+a.tot,b.G[i].v+a.tot,b.G[i].w});
              ~^~~~~~~~~~~
/in/foo.cc:60:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<G.size();i++)
              ~^~~~~~~~~
/in/foo.cc: In function 'll query(MST)':
/in/foo.cc:74:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.G.size();i++)ret+=a.G[i].w;
              ~^~~~~~~~~~~