string min_express(string& s) {int n = s.size();if(n == 0) return s;int i = 0, j = 1, k = 0;while(k < n && i < n && j < n) {if(s[(i + k) % n] == s[(j + k) % n]) k ++;else {s[(i + k) % n] > s[(j + k) % n] ? i += k + 1 : j += k + 1;if(i == j) i ++;k = 0;}}i = min(i, j);return s.substr(i) + s.substr(0, i);}
