/in/foo.cc: In function 'int main()':
/in/foo.cc:9:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0;i < a.size();i++)
                 ~~^~~~~~~~~~
/in/foo.cc:11:20: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = 0;j < a[0].size();j++)
                  ~~^~~~~~~~~~~~~
/in/foo.cc:19:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for (int i = 0;i < a.size()-1&&tar==1;i++)
                 ~~^~~~~~~~~~~~
/in/foo.cc:21:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for (int j = i+1;j < a.size()&&tar==1;j++)
                    ~~^~~~~~~~~~
/in/foo.cc:24:12: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for (;k < a[0].size();k++)
          ~~^~~~~~~~~~~~~
/in/foo.cc:29:8: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    if(k== a[0].size())
       ~^~~~~~~~~~~~~~