Compilare: main.c: In function 'main': main.c:34:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.in", "r", stdin); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:35:5: warning: ignoring return value of 'freopen', declared with attribute warn_unused_result [-Wunused-result] freopen("dfs.out", "w", stdout); ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ main.c:37:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%lld", &n, &m); ^~~~~~~~~~~~~~~~~~~~~~~ main.c:40:9: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result] scanf("%d%d", &x, &y); ^~~~~~~~~~~~~~~~~~~~~