Compilare: user.cpp: In function ‘int main()’: user.cpp:61:31: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘std::vector<std::vector<int> >::size_type {aka unsigned int}’ [-Wformat=] printf("%lu\n", sol.size()); ^ user.cpp:44:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("biconex.in", "r", stdin); ^ user.cpp:45:41: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen ("biconex.out", "w", stdout); ^ user.cpp:48:26: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i%i", &n, &m); ^ user.cpp:52:30: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%i%i", &x, &y); ^