A number is ugly number in C# if it's product of 2, 3 and 5. This function finds nth ugly number using brute force approach.

UglyNumberNaive.cs

public static int PowerRemainder(int n, int divisor) 
{ 
    while((n%divisor) == 0)
    {
        n /= divisor;
    }
    return n;
}

public static int UglyNumberNth(int n)
{
    if(n<=0)
    {
        throw new ArgumentOutOfRangeException();
    }

    int count = 1;
    int i = 2;

    while(count < n)
    {
        int temp = PowerRemainder(i, 2);
        temp = PowerRemainder(temp, 3);
        temp = PowerRemainder(temp, 5);
        if (temp == 1)
        {
            count++;
        }
        i++;
    }

    return i;
}