/in/foo.cc: In function 'int judge(int, int)':
/in/foo.cc:12:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=x+1;i<a.size();i++)
                   ~^~~~~~~~~
/in/foo.cc: In function 'void dfs(int, int, int)':
/in/foo.cc:18:9: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(t==a.size()-1)
        ~^~~~~~~~~~~~
/in/foo.cc:28:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     for(int i=t+1;i<a.size();i++)
                   ~^~~~~~~~~