/in/foo.cc: In function 'int F()':
/in/foo.cc:6:6: error: 'n' was not declared in this scope
  if (n < 1)
      ^
/in/foo.cc:8:6: error: 'n' was not declared in this scope
  if (n == 1)
      ^
/in/foo.cc:10:6: error: 'n' was not declared in this scope
  if (n == 2)
      ^
/in/foo.cc:15:29: error: 'n' was not declared in this scope
  for (long long i = 3; i <= n; i++)
                             ^