foo.c: In function 'main':
foo.c:7:16: warning: variable 'b' set but not used [-Wunused-but-set-variable]
    7 |  int i,j,k,n,a,b;
      |                ^
foo.c:7:10: warning: unused variable 'k' [-Wunused-variable]
    7 |  int i,j,k,n,a,b;
      |          ^
foo.c:8:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    8 |  scanf("%d", &n);
      |  ^~~~~~~~~~~~~~~
foo.c:11:3: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
   11 |   scanf("%d", &s[i][0]);
      |   ^~~~~~~~~~~~~~~~~~~~~

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