Compilare: user.cpp: In function ‘int main()’: user.cpp:123:33: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘std::vector<int>::size_type {aka unsigned int}’ [-Wformat=] printf("%lu\n", solution.size()); ^ user.cpp:88:51: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen((file_input + ".in").c_str(), "r", stdin); ^ user.cpp:89:53: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen((file_input + ".out").c_str(), "w", stdout); ^