Compilare: user.cpp: In function ‘void bk(int)’: user.cpp:90:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(k==v.size()) ^ user.cpp: In function ‘int main()’: user.cpp:117:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a1.size();i++) ^ user.cpp:124:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0;i<a2.size();i++) ^