Compilare: main.cpp: In function 'int main()': main.cpp:14:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:18:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ~^~~~~~~~~ main.cpp:30:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(i=0;i<s.size();i++) ~^~~~~~~~~