Compilare: user.c: In function ‘main’: user.c:19:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(InFile,"r",stdin); ^ user.c:20:12: warning: ignoring return value of ‘freopen’, declared with attribute warn_unused_result [-Wunused-result] freopen(OutFile,"w",stdout); ^ user.c:23:10: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result [-Wunused-result] scanf("%d %d",&N,&M); ^ user.c:24:9: warning: ignoring return value of ‘gets’, declared with attribute warn_unused_result [-Wunused-result] gets(lin); ^ user.c:27:13: warning: ignoring return value of ‘gets’, declared with attribute warn_unused_result [-Wunused-result] gets(lin); ^ /tmp/ccpBpBxD.o: In function `main': user.c:(.text.startup+0x74): warning: the `gets' function is dangerous and should not be used.