/in/foo.cc: In function 'int main()':
/in/foo.cc:9:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<a.size();)
              ~^~~~~~~~~
/in/foo.cc:12:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int j=i;j<i+b.size();j++)
               ~^~~~~~~~~~~
/in/foo.cc:22:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
    for(int k=0;k<c.size();k++)
                ~^~~~~~~~~