Compilare: user.cpp: In function ‘int main()’: user.cpp:32:21: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if(S.size() > d) ~~~~~~~~~^~~ user.cpp:15:44: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("slidingwindow.in", "r", stdin); ^ user.cpp:16:46: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("slidingwindow.out", "w", stdout); ^ user.cpp:17:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &d); ^ user.cpp:19:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i]); ^