delNum

#include <iostream>

int main()
{
    int num{ 0 };
    int delNum{ 0 };
    int pos{1};
    int digit{ 0 };
    int mult{ 1 };

    std::cout << "Enter number: ";
    std::cin >> num;
    num > 0 ? pos = 1 : pos = -1;
    num *= pos;

    while (num)
    {
        digit = num % 10;
        num /= 10;
        if (digit != 3 and digit != 6)
        {
            delNum += digit * mult;
            mult *= 10;
        }
    }

    std::cout << "Corrected (maybe) number: " << delNum * pos << "\n";
}