Compilare: user.cpp: In function ‘int Find(int, std::vector<int>&)’: user.cpp:15:29: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(; step < v.size() - 1; step <<= 1); ^ user.cpp:19:31: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if((i + step < v.size()) && (v[i + step] <= idx) && (s[v[i + step]] == x)) ^ user.cpp: In function ‘int main()’: user.cpp:30:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("undo2.in","r",stdin); ^ user.cpp:31:36: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("undo2.out","w",stdout); ^ user.cpp:33:20: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &N); ^ user.cpp:37:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &Q, &x); ^