binTodecSimpleForDebug

#include <iostream>

int main()
{
    int bin{ 0 };
    int dec{ 0 };
    std::cin >> bin;

    for (int mul{ 1 }, bit{ 0 }; bin; mul *= 2, bin /= 10)
    {
        bit = bin % 10;
        if (bit != 0 and bit != 1)
        {
            std::cout << "Bad number!\n";
            return 1;
        }
        dec += bit * mul;
    }

    std::cout << "Decimal number: " << dec << '\n';
}