Compilare: user.cpp: In function ‘int main()’: user.cpp:73:34: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘std::vector<std::stack<int> >::size_type {aka unsigned int}’ [-Wformat=] printf("%lu\n", solution.size()); ^ user.cpp: In function ‘void readInput()’: user.cpp:18:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.in", "r", stdin); ^ user.cpp:19:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("ctc.out", "w", stdout); ^ user.cpp:21:25: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ user.cpp:23:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &a, &b); ^