Compilare: main.cpp: In function 'int main()': main.cpp:14:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i < a.length(); i++) { ~~^~~~~~~~~~~~ main.cpp:23:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 0; i < b.length(); i++) { ~~^~~~~~~~~~~~ main.cpp:27:14: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == a.length()) { ~~^~~~~~~~~~~~~