/in/foo.cc: In function 'int main()':
/in/foo.cc:60:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0; i<exist[x].size(); i++)
                 ~^~~~~~~~~~~~~~~~
/in/foo.cc:89:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int i=0; i<exist[L].size(); i++)
                 ~^~~~~~~~~~~~~~~~
/in/foo.cc:92:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<exist[R].size(); i++)
                  ~^~~~~~~~~~~~~~~~
/in/foo.cc:94:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=0; i<exist[L].size(); i++)
                  ~^~~~~~~~~~~~~~~~