МИФИ ПИДОРЫ

#include <iostream>
#include <algorithm>
#include <cmath>
using namespace std;
int to10(int from, string number)
{
    int number10 = 0;
    int degree = 0;
    for (int i = number.length() - 1; i >= 0; i--)
    {
        if (number[i] <= '9')
        {
            if (number[i] - 48 >= from || number[i] < 48)
            {
                cout << "ERROR";
                return 0;
            }
            number10 += (number[i] - 48) * pow(from, degree);
        }
        else
        {
            if (number[i] - 55 >= from || number[i] > 90)
            {
                cout << "ERROR";
                return 0;
            }
            number10 += (number[i] - 55) * pow(from, degree);
        }
        degree++;
    }

}
string togiven(int number10, int to)
{
    string numberto;
    while(number10 > 0)
    {
        if (number10 % to <= '9')
            numberto += number10 % to + 48;
        else
            numberto += number10 % to + 55;
        number10 /= to;
    }
    std :: reverse(numberto.begin(), numberto.end());
    return numberto;
}
int main()
{
    int from, to;
    string number;
    cin >> from;
    cin >> to;
    cin >> number;
    if (number == "0" || number == "1")
    {
        cout << number;
        return 0;
    }
    int number10 = to10(from, number);
    string numberto = togiven(number10, to);
    cout << numberto;
}