int ReplAllDigCofAwithB(int A, int C, int B)
{
    if (A<=0 || C<0 || C>9 || B<0 || B>9) return -1;
    int result=0, multiplier=1;
    while (A>0)
    {
        int digit=A%10;
        if (digit==C) digit=B;
        result = digit*multiplier + result;
        multiplier*=10;
        A/=10;
    }
    return result;
}