--- 
+++ 
@@ -39,6 +39,8 @@
 	fread(&magic, 4, 1, f);
 	bool ok = (magic == 0x0101FFFF);
 	printf("Magic %08x check %i : %s\n", magic, no, ok ? "ok" : "not ok");
+	if(!ok)
+		printf("current pos : 0x%08x\n", ftell(f));
 	return ok;
 }