首先读取一串列标号，这些列标号成对出现，表示输入行的列范围。这串列标号以一个负值结尾，作为结束标志。剩余的输入行被程序读入并打印，然后输入行中被选中范围的字符串被提取出来并打印。注意，每行第1列的列标号为零-First reads a serial label, label these columns appear in pairs, which means input line column range. This serial label with a negative end, as th