/in/foo.cc: In function 'void build(int, int, int)':
/in/foo.cc:28:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0; i<exist[cnt].size(); i++)First[cnt][exist[cnt][i]]=Last[cnt][exist[cnt][i]]=0;
               ~^~~~~~~~~~~~~~~~~~
/in/foo.cc: In function 'int main()':
/in/foo.cc:59:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0; i<exist[x].size(); i++)
                 ~^~~~~~~~~~~~~~~~
/in/foo.cc:88:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0; i<exist[L].size(); i++)
                 ~^~~~~~~~~~~~~~~~
/in/foo.cc:91:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<exist[R].size(); i++)
                  ~^~~~~~~~~~~~~~~~
/in/foo.cc:93:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<exist[L].size(); i++)
                  ~^~~~~~~~~~~~~~~~