/in/foo.cc: In function 'void solve1(int, int)':
/in/foo.cc:45:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < s1[u].size(); i++) buf[s1[u][i]]++;
                 ~~^~~~~~~~~~~~~~
/in/foo.cc:48:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < e1[u].size(); i++) buf[e1[u][i]]--;
                 ~~^~~~~~~~~~~~~~
/in/foo.cc: In function 'void solve2(int, int)':
/in/foo.cc:52:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < s2[u].size(); i++) buf[s2[u][i]]++;
                 ~~^~~~~~~~~~~~~~
/in/foo.cc:55:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i = 0; i < e2[u].size(); i++) buf[e2[u][i]]--;
                 ~~^~~~~~~~~~~~~~