Compilare: user.cpp: In function ‘void load(int, int)’: user.cpp:11:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = l; i <= r && i < str.size(); ++ i) ^ user.cpp: In function ‘int main()’: user.cpp:21:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int period = 1; period <= min(26U, str.size()); ++ period) { ^ user.cpp:26:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (start < str.size()) { ^