Compilare: main.cpp: In function 'int main()': main.cpp:25:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size() - 2; ++i) { ~~^~~~~~~~~~~~~~ main.cpp:30:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < s.size(); i++) { ~~^~~~~~~~~~ main.cpp:35:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int k = 4; k <= s.size(); ++k) { ~~^~~~~~~~~~~ main.cpp:36:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < s.size(); ++i) { ~~^~~~~~~~~~ main.cpp:38:26: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(right < s.size()) { ~~~~~~^~~~~~~~~~