Compilare: main.cpp: In function 'int main()': main.cpp:12:24: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; 3*i <= s.length(); i++) { ~~~~^~~~~~~~~~~~~ main.cpp:14:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j *2*i < s.size(); j++) ~~~~~~~^~~~~~~~~~