Eroare de compilare: user.cpp: In function ‘int valid(int)’: user.cpp:16:9: warning: unused variable ‘i’ [-Wunused-variable] int i; ^ user.cpp: In function ‘void prelsol()’: user.cpp:25:9: warning: unused variable ‘i’ [-Wunused-variable] int i; ^ user.cpp: In function ‘int main()’: user.cpp:57:15: error: variable ‘std::ifstream f’ has initializer but incomplete type ifstream f("") ^ user.cpp:58:5: error: expected ‘,’ or ‘;’ before ‘back’ back(); ^