Compilare: user.cpp: In function ‘int main()’: user.cpp:42:33: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("java.in","r",stdin); ^ user.cpp:43:35: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("java.out","w",stdout); ^ user.cpp:44:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d\n",&t); ^ user.cpp:49:37: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d\n",&n,&m,&l); ^ user.cpp:65:20: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s); ^ user.cpp:79:29: warning: ‘a’ may be used uninitialized in this function [-Wmaybe-uninitialized] v[a].push_back(b); ^ /tmp/ccLynIHx.o: In function `main': user.cpp:(.text.startup+0x14c): warning: the `gets' function is dangerous and should not be used.