Compilare: user.cpp: In function ‘int main()’: user.cpp:63:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = 0; k < s.size(); ++k) { ~~^~~~~~~~~~ user.cpp:75:27: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int k = 0; k < s.size(); ++k) { ~~^~~~~~~~~~ user.cpp:85:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int delta = 1; delta < s.size(); ++delta) { ~~~~~~^~~~~~~~~~ user.cpp:86:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int let0 = 0; let0 + delta < s.size(); ++let0) { ~~~~~~~~~~~~~^~~~~~~~~~