Compilare: main.cpp: In function 'int main()': main.cpp:19:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i <= a.size(); i++) ~~^~~~~~~~~~~ main.cpp:22:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = a.size()+2; i < s.size(); i++) ~~^~~~~~~~~~