Compilare: user.cpp: In function ‘int main()’: user.cpp:20:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(!s.empty() && s.size()+n-1-i >= k && di[i] > s.top()) ^ user.cpp:12:38: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alibaba.in", "r", stdin); ^ user.cpp:13:40: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("alibaba.out", "w", stdout); ^ user.cpp:15:34: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d\n%s", &n, &k, di); ^