#include <iostream>
#include <queue>
#include <unordered_map>

int main()
{
    std::string a = "0110";
    std::string b = "1101";
    int n = a.length();

    std::queue<std::string> state;
    state.push(a);
    std::unordered_map<std::string, int> oper;
    oper[a] = 0;
    while (!state.empty())
    {
        std::string s = state.front();
        state.pop();
        int ops = oper[s] + 1;
        for (int l = 0; l < n; ++l)
        {
            for (int r = l; r < n; ++r) // reversing
            {
                s[r] = '1' - s[r] + '0';
                if (oper.find(s) == oper.end())
                {
                    state.push(s);
                    oper[s] = ops;
                }
            }
            for (int j = l; j < n; ++j) // reversing back
            {
                s[j] = '1' - s[j] + '0';
            }
        }
    }
    std::cout << oper[b];
    return 0;
}