Compilare: user.cpp: In function ‘void read()’: user.cpp:44:9: warning: unused variable ‘i’ [-Wunused-variable] int i; ^ user.cpp:45:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("div4.in", "r", stdin); ^ user.cpp:46:16: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s + 1); ^ user.cpp:47:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &k); ^ user.cpp: In function ‘void write()’: user.cpp:88:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("div4.out", "w", stdout); ^ /tmp/cccpe7vN.o: In function `read()': user.cpp:(.text+0x1e0): warning: the `gets' function is dangerous and should not be used.