/in/foo.cc: In function 'int main()':
/in/foo.cc:66:28: error: 'pow' was not declared in this scope
             if(i%2) sum -= pow(10,i) -1;
                            ^~~
/in/foo.cc:66:28: note: suggested alternative: 'putw'
             if(i%2) sum -= pow(10,i) -1;
                            ^~~
                            putw