import std.stdio;

bool divisibleBy1to20(immutable int x) pure nothrow @safe
{
    // We already know that this number is divisible by 20 and everything under 11
    const nums = [11,12,13,14,15,16,17,18,19];
    foreach(int i; nums)
    {
        if(x % i != 0)
            return false;
    }
    return true;
}

unittest
{
    assert(divisibleBy1to20(20) == false);
    assert(divisibleBy1to20(19) == false);
    assert(divisibleBy1to20(1) == false);
    assert(divisibleBy1to20(-1) == false);
    assert(divisibleBy1to20(-20) == false);
    assert(divisibleBy1to20(232792560) == true);
}

int main()
{
    int i = 20;
    while(!divisibleBy1to20(i))
    {
        i=i+20;
    }
    writefln("The smallest positive number that is evenly divisible by all of the numbers from 1 to 20 is %d.",i);
    return 0;
}