/in/foo.cc: In function 'int main()':
/in/foo.cc:10:8: error: 'a' was not declared in this scope
  sort (a,a+20);
        ^
/in/foo.cc:18:16: error: 'pick' was not declared in this scope
    for(pickB=1;pick<=n;pickB++)
                ^~~~
/in/foo.cc:18:16: note: suggested alternative: 'pickB'
    for(pickB=1;pick<=n;pickB++)
                ^~~~
                pickB