Compilare: user.cpp: In function ‘int main()’: user.cpp:23:67: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (!S.empty() && digits[i] > S.back() && S.size() + N - i > M) { ^ user.cpp:14:7: warning: unused variable ‘x’ [-Wunused-variable] char x; ^ user.cpp:19:31: warning: ignoring return value of ‘int fscanf(FILE*, const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] fscanf(fin, "%d %d ", &N, &M); ^ user.cpp:20:35: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(digits, sizeof digits, fin); ^