```calc
grade(U) :=
  "OK" if U <= 1
  "fails" otherwise
grade(0.8) = ?
grade(1.2) = ?
```

```calc
fib(n) :=
  a <- 0
  b <- 1
  for k in 1..n
    t <- a + b
    a <- b
    b <- t
  a
fib(10) = ?
```