foo.c: In function 'main':
foo.c:10:10: error: 'f' undeclared (first use in this function)
   10 |   t=sqrt(f)+1;
      |          ^
foo.c:10:10: note: each undeclared identifier is reported only once for each function it appears in
foo.c:6:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
    6 |  scanf("%d",&i);
      |  ^~~~~~~~~~~~~~

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