Compilare: user.cpp: In function ‘int main()’: user.cpp:12:28: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int i=0; i<=a.size();++i) ^ user.cpp:14:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(a[i]==b[j] && i<a.size()) ^ user.cpp:11:9: warning: unused variable ‘i’ [-Wunused-variable] int i, j=0; ^