Compilare: user.cpp: In function ‘int main()’: user.cpp:30:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int l = 1; l * 3 <= txt.size(); ++l) { ^ user.cpp:39:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int st = 1; st + l - 1 < txt.size(); ++st) { ^ user.cpp:47:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int st = 0; st + l + l < txt.size(); ++st) ^