/in/foo.cc: In function 'int main()':
/in/foo.cc:15:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(i>=0 && i<A.size()) 
                ~^~~~~~~~~
/in/foo.cc:22:17: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]
     if(i>=0 && i<A.size()) A.erase(A.begin()+i);
                ~^~~~~~~~~
/in/foo.cc:5:11: warning: unused variable 'n' [-Wunused-variable]
       int n,i,x;
           ^