A bug in the functionceil

[DOFYPXY]

If the input of the ceil function is an integer x(that is, x modulo FRACT_PART is equal to 0), it will return x+1. But I think this does not match the usual semantics of ceil function in mathematics.

The bug is found by Medjai, a symbolic execution tool for the Cairo program. The spec we write for ceil is:

func ceil_spec{range_check_ptr}():
    alloc_locals
    let (local x) = SymbolicMath64x61()
    let (local res) = Math64x61.ceil(x)
    verify_le_signed(x, res)
    verify_lt_signed(res - Math64x61.ONE, x)
    let (_, rem) = signed_div_rem(res, Math64x61.ONE, Math64x61.BOUND)
    medjai_assert_eq_felt(rem, 0)
    return ()
end