Compilare: user.cpp: In function ‘int main()’: user.cpp:25:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = n + 1; i < S.size(); i++) ^ user.cpp:33:37: warning: suggest parentheses around ‘+’ inside ‘<<’ [-Wparentheses] for (int i = 0; i < (1 << n + 1) && !w; i++) { ^ user.cpp:47:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (Sol.size() < n) fout << 'a', n--; ^