Compilare: main.cpp: In function 'int main()': main.cpp:14:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i<a.size(); ++i) ~^~~~~~~~~ main.cpp:30:25: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = start; i<a.size(); ++i) ~^~~~~~~~~ main.cpp:43:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(i < a.size() && a[i] >= 'a' && a[i] <= 'z') ~~^~~~~~~~~~