foo.c: In function 'main':
foo.c:16:3: warning: statement with no effect [-Wunused-value]
   for (m;m>=1;m--){
   ^~~
foo.c:9:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%d %d",&l,&m);
   ^~~~~~~~~~~~~~~~~~~~
foo.c:13:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d %d",&num[i],&num[i+1]);/*奇数储存起始段，偶数储存终止端*/
     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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