/in/foo.c: In function 'main':
/in/foo.c:39:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d", &N);
  ^
/in/foo.c:41:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%s", M);//M 数字 
  ^