local function semiprime(n)
    if n < 3 then return false end
    local nf = 0
    for i = 2, n do
        while n % i == 0 do
            if nf == 2 then return false end
            nf += 1
            n //= i
        end
    end
    return nf == 2
end

for v = 1675, 1680 do
    print($"{v} -> {semiprime(v) ? "is" : "isn't"} semi-prime")
end