/in/foo.cc: In function 'int main()':
/in/foo.cc:5:30: warning: unused variable 'k' [-Wunused-variable]
 {   int n(n<20); cin>>n; int k=0;
                              ^
/in/foo.cc:5:12: warning: 'n' is used uninitialized in this function [-Wuninitialized]
 {   int n(n<20); cin>>n; int k=0;
           ~^~~