Eroare de compilare: user.cpp: In function ‘int main()’: user.cpp:17: error: ‘ifstream’ was not declared in this scope user.cpp:17: error: expected ‘;’ before ‘fin’ user.cpp:18: error: ‘ofstream’ was not declared in this scope user.cpp:18: error: expected ‘;’ before ‘fout’ user.cpp:21: error: ‘fin’ was not declared in this scope user.cpp:31: error: ‘fout’ was not declared in this scope user.cpp:34: error: ‘fout’ was not declared in this scope user.cpp: In function ‘int back()’: user.cpp:66: warning: the address of ‘int valid(int, int)’ will always evaluate as ‘true’ user.cpp:49: warning: unused variable ‘i’ user.cpp:49: warning: unused variable ‘j’ user.cpp:50: warning: unused variable ‘aux’