Compilare: main.cpp: In function 'int main()': main.cpp:27:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1 ; i*3 <= s.size() ; i++) ~~~~^~~~~~~~~~~ main.cpp:33:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0 ; j + 2*i < s.size() ; j++) ~~~~~~~~^~~~~~~~~~