Compilare: user.cpp: In function ‘void df(int)’: user.cpp:23:35: 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:53:40: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < at[i].size(); j++) { ^ user.cpp:67:47: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < a[q.front()].size(); i++) { ^ user.cpp:77:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 1; i < top.size(); i++) { ^ user.cpp:81:45: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int j = 0; j < at[top[i]].size(); j++) { ^ user.cpp:99:34: warning: comparison between signed and unsigned integer expressions [-Wsign-compare] for (int i = 0; i < ans.size(); i++) { ^ user.cpp:29:37: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("marvel.in", "r", stdin); ^ user.cpp:30:39: warning: ignoring return value of ‘FILE* freopen(const char*, const char*, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] freopen("marvel.out", "w", stdout); ^ user.cpp:32:41: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d %d %d", &n, &m, &k, &p); ^ user.cpp:34:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &v[i]); ^ user.cpp:37:27: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d", &w[i]); ^ user.cpp:41:31: warning: ignoring return value of ‘int scanf(const char*, ...)’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d", &x, &y); ^