foo.c: In function 'main':
foo.c:12:10: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int n,m;scanf("%d%d",&n,&m);//n行m列 
          ^~~~~~~~~~~~~~~~~~~
foo.c:16:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&a[i][j]);
    ^~~~~~~~~~~~~~~~~~~~
foo.c:19:4: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    scanf("%d",&b[i][j]);  
    ^~~~~~~~~~~~~~~~~~~~
foo.c:20:16: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  int r,c,k,l=0;scanf("%d%d%d",&r,&c,&k);
                ^~~~~~~~~~~~~~~~~~~~~~~~

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