Compilare: user.cpp: In function ‘long long int lucas(long long int, long long int, long long int)’: user.cpp:58:44: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < min(x.size(), y.size()); ++i) ^ user.cpp: In function ‘int main()’: user.cpp:72:6: warning: variable ‘lm’ set but not used [-Wunused-but-set-variable] int lm = 0; ^