Compilare: main.cpp: In function 'int main()': main.cpp:48:22: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] if (v.size() <= k) { ~~~~~~~~~^~~~ main.cpp:58:42: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i <= n && ans.size() < k; ++i) ~~~~~~~~~~~^~~ main.cpp:34:38: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("salvare.in", "r", stdin); ^ main.cpp:35:40: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)', declared with attribute warn_unused_result [-Wunused-result] freopen("salvare.out", "w", stdout); ^ main.cpp:36:27: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &k); ^ main.cpp:39:31: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^