Compilare: user.cpp: In function 'void df(int)': user.cpp:26: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'void append(std::vector<int, std::allocator<int> >&, std::vector<int, std::allocator<int> >&)': user.cpp:52: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'int main()': user.cpp:80: warning: unused variable 'size' user.cpp:90: warning: comparison between signed and unsigned integer expressions user.cpp:93: warning: comparison between signed and unsigned integer expressions