Compilare: user.cpp: In function ‘int main()’: user.cpp:23:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] while (!D.empty() && D.size() - j >= l) { ^ user.cpp:38:18: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (D.size() > u) { ^ user.cpp:43:19: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (D.size() >= l && D.size() <= u && sum > sol) ^ user.cpp:43:36: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (D.size() >= l && D.size() <= u && sum > sol) ^ user.cpp:14:32: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sum2.in", "r", stdin); ^ user.cpp:15:34: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("sum2.out", "w", stdout); ^ user.cpp:17:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &n, &l, &u); ^ user.cpp:20:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &nums[i]); ^