Compilare: user.cpp: In function ‘int main()’: user.cpp:14:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b.size(); i ++) ~~^~~~~~~~~~ user.cpp:16:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i ++) ~~^~~~~~~~~~ user.cpp:18:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < b.size(); i ++) { ~~^~~~~~~~~~ user.cpp:24:23: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a.size(); i ++) { ~~^~~~~~~~~~ user.cpp:35:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i = 1; i <= b.size(); i ++) ~~^~~~~~~~~~~