/in/foo.cc: In function 'int main()':
/in/foo.cc:19:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             while(p1<v[i].size()&&p2<v[j].size()){
                   ~~^~~~~~~~~~~~
/in/foo.cc:19:37: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
             while(p1<v[i].size()&&p2<v[j].size()){
                                   ~~^~~~~~~~~~~~
/in/foo.cc:22:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     while(p1<v[i].size()&&v[i][p1]<sec)p1++;
                           ~~^~~~~~~~~~~~
/in/foo.cc:23:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     if(p1<v[i].size()){
                        ~~^~~~~~~~~~~~
/in/foo.cc:31:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     while(p2<v[j].size()&&v[j][p2]<fir)p2++;
                           ~~^~~~~~~~~~~~
/in/foo.cc:32:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
                     if(p2<v[j].size()){
                        ~~^~~~~~~~~~~~