Compilare: user.cpp: In function ‘int main()’: user.cpp:60:45: warning: format ‘%lu’ expects argument of type ‘long unsigned int’, but argument 2 has type ‘std::basic_string<char>::size_type {aka unsigned int}’ [-Wformat=] printf("%lu\n%s", sir.length(), sir.c_str()); ^ user.cpp:16:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biti.in", "r", stdin); ^ user.cpp:17:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("biti.out", "w", stdout); ^ user.cpp:19:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] int n; scanf("%d", &n); ^