/in/foo.cc: In function 'int main()':
/in/foo.cc:17:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if(A[i].size()<j+1) A[i].resize(j+1);
       ~~~~~~~~~~~^~~~
/in/foo.cc:22:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
      if(A[i].size()<j+1)
         ~~~~~~~~~~~^~~~