Compilare: user.cpp: In function ‘int main()’: user.cpp:46:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("car.in", "r", stdin); ^ user.cpp:47:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("car.out", "w", stdout); ^ user.cpp:49:29: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n", &n, &m); ^ user.cpp:50:47: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d\n", &xi, &yi, &xf, &yf); ^ user.cpp:56:19: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(ch+1); ^ /tmp/cc43bF0C.o: In function `main': user.cpp:(.text.startup+0xe8): warning: the `gets' function is dangerous and should not be used.