Compilare: user.cpp: In function 'void back(long unsigned int, long unsigned int, int)': user.cpp:21: warning: comparison between signed and unsigned integer expressions user.cpp:25: warning: comparison between signed and unsigned integer expressions user.cpp: In function 'int main()': user.cpp:35: warning: format '%lld' expects type 'long long int*', but argument 3 has type 'long unsigned int*' user.cpp:35: warning: format '%lld' expects type 'long long int*', but argument 4 has type 'long unsigned int*' user.cpp:35: warning: format '%lld' expects type 'long long int*', but argument 5 has type 'long unsigned int*' user.cpp:45: warning: format '%s' expects type 'char*', but argument 3 has type 'char (*)[31]' user.cpp:54: warning: format '%lld' expects type 'long long int', but argument 3 has type 'long unsigned int'