Lyndon - Duval

int solve(const string &s)
{
    string t = s + s;
    int n = s.size();
    int res = 0;

    for (int l = 0; l < n; )
    {
        res = l;
        int r = l, p = l + 1;
        for (; r < n && s[r] <= s[p]; ++r, ++p)
            if (s[r] < s[p]) r = l - 1;

        while (l <= r) l += p - r;
    }

    return res;
}