Compilare: user.cpp: In function ‘int main()’: user.cpp:72:30: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < v.size(); ++i) { ^ user.cpp:73:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = i + 1; j < v.size(); ++j) { ^