/in/foo.cc: In function 'int check(std::vector<int>)':
/in/foo.cc:13:15: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
  for(int i=0;i<v.size();i++)
              ~^~~~~~~~~
/in/foo.cc:11:18: warning: unused variable 'd' [-Wunused-variable]
  int a=0,b=0,c=0,d=0;
                  ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:38:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v.size();i++)
               ~^~~~~~~~~
/in/foo.cc:48:16: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
   for(int i=0;i<v.size();i++)
               ~^~~~~~~~~