Compilare: user.cpp: In function ‘int main()’: user.cpp:25:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 2; i <= a.size(); i++) { ^ user.cpp:38:32: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i <= b.size(); i++) { ^ user.cpp:45:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k == a.size() - 1) { ^