foo.c: In function 'main':
foo.c:29:6: error: 'i' undeclared (first use in this function)
   29 |  for(i=1;i<=n;i++)
      |      ^
foo.c:29:6: note: each undeclared identifier is reported only once for each function it appears in
foo.c:31:7: error: 'j' undeclared (first use in this function)
   31 |   for(j=1;j<=n;j++)
      |       ^
foo.c:43:6: warning: unused variable 'j' [-Wunused-variable]
   43 |  int j;
      |      ^
foo.c:42:6: warning: unused variable 'i' [-Wunused-variable]
   42 |  int i;
      |      ^

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