Compilare: user.cpp: In function ‘void df(int, int)’: user.cpp:18:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[x].size(); i++) { ^ user.cpp:34:35: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[x].size(); i++) { ^ user.cpp: In function ‘int main()’: user.cpp:47:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("posta2.in", "r", stdin); ^ user.cpp:48:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("posta2.out", "w", stdout); ^ user.cpp:50:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &n, &m); ^ user.cpp:52:38: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d", &x, &y, &w); ^ user.cpp:61:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &v[i]); ^ user.cpp:67:24: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &x); ^ user.cpp:72:17: warning: ‘first’ may be used uninitialized in this function [-Wmaybe-uninitialized] df(first, 0); ^