foo.c: In function 'main':
foo.c:10:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d",&n);
  ^~~~~~~~~~~~~~
foo.c:9:11: warning: iteration 99 invokes undefined behavior [-Waggressive-loop-optimizations]
  {a[i+2]=a[i+1]+a[i];}
          ~^~~~~
foo.c:8:2: note: within this loop
  for(i=0;i<100;i++)
  ^~~

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