Compilare: user.cpp: In function ‘void read()’: user.cpp:108:12: warning: unused variable ‘j’ [-Wunused-variable] int i, j, val; ^ user.cpp:105:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("zumzi.in", "r", stdin); ^ user.cpp:106:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &n, &m, &k, &x); ^ user.cpp:114:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &val); ^ user.cpp: In function ‘void write()’: user.cpp:150:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("zumzi.out", "w", stdout); ^