Compilare: user.cpp: In function ‘void euler(int)’: user.cpp:24:9: warning: unused variable ‘last’ [-Wunused-variable] int last; ^ user.cpp: In function ‘int main()’: user.cpp:59:41: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < cycle.size () - 1; i++) ^