Compilare: user.cpp: In function ‘int main()’: user.cpp:35:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for(int j = 0; j < l[i].size(); ++j) ^ user.cpp:15:30: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pq.in", "r", stdin); ^ user.cpp:16:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("pq.out", "w", stdout); ^ user.cpp:17:23: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &n, &q); ^ user.cpp:19:21: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &a[i]); ^ user.cpp:31:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &L, &R); ^