Compilare: user.cpp: In function ‘int main()’: user.cpp:22:69: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while(!st.empty() && st.top() < s[i] && st.size() + n-i >= k) st.pop(); ^ user.cpp:14:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trompeta.in","r",stdin); ^ user.cpp:15:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("trompeta.out","w",stdout); ^ user.cpp:16:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d\n",&n,&k); ^ user.cpp:17:11: warning: ignoring return value of ‘char* gets(char*)’, declared with attribute warn_unused_result [-Wunused-result] gets(s+1); ^ /tmp/ccdrDJL7.o: In function `main': user.cpp:(.text.startup+0x77): warning: the `gets' function is dangerous and should not be used.