Compilare: user.cpp: In function ‘void set(int, int, int)’: user.cpp:25:20: warning: array subscript has type ‘char’ [-Wchar-subscripts] v[lin][l[lin]++] = make_pair (make_pair (x, y), val); ^ user.cpp: In function ‘int main()’: user.cpp:94:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("sccm.in", "r", stdin); ^ user.cpp:95:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("sccm.out", "w", stdout); ^ user.cpp:97:26: 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:98:21: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (sir+1), po = 1; ^ user.cpp:105:21: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets (sir+1), po = 1; ^ /tmp/cc4Z722F.o: In function `main': user.cpp:(.text.startup+0x85): warning: the `gets' function is dangerous and should not be used.