/in/foo.cc: In function 'int jf(int)':
/in/foo.cc:22:30: error: 'pow' was not declared in this scope
   c += a[i] * pow(jz, (n - i));
                              ^
/in/foo.cc:24:26: error: 'pow' was not declared in this scope
   b += a[i] * pow(jz, i-1);
                          ^