Compilare: user.cpp: In function ‘int main()’: user.cpp:72:30: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘std::queue<int>::size_type {aka unsigned int}’ [-Wformat=] printf ("%lu\n", Q.size()); ^ user.cpp:36:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("graf.in", "r", stdin); ^ user.cpp:37:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("graf.out", "w", stdout); ^ user.cpp:38:43: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf ("%d%d%d%d\n", &n, &m, &xi, &xf); ^ user.cpp:41:22: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (parser); ^ /tmp/ccMzc2pe.o: In function `main': user.cpp:(.text.startup+0xa0): warning: the `gets' function is dangerous and should not be used.