Compilare: user.cpp: In function ‘void df(int)’: user.cpp:26: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void euler(int)’: user.cpp:32: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:98: warning: comparison between signed and unsigned integer expressions user.cpp:101: warning: comparison between signed and unsigned integer expressions