Compilare: user.cpp: In function ‘void back(int)’: user.cpp:15:9: warning: unused variable ‘i’ [-Wunused-variable] int i; ^ user.cpp: In function ‘int main()’: user.cpp:29:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("preasimplu.in","r",stdin); ^ user.cpp:30:42: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("preasimplu.out","w",stdout); ^ user.cpp:31:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d", &t); ^ user.cpp:34:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d %d %d", &n, &k, &MOD); ^