Compilare: user.cpp: In function ‘void df(int)’: user.cpp:25: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘void euler(int)’: user.cpp:31: warning: comparison between signed and unsigned integer expressions user.cpp: In function ‘int main()’: user.cpp:83: warning: comparison between signed and unsigned integer expressions user.cpp:86: warning: comparison between signed and unsigned integer expressions