foo.c:3:6: warning: return type of 'main' is not 'int' [-Wmain]
    3 | void main()
      |      ^~~~
foo.c: In function 'main':
foo.c:21:17: error: 'else' without a previous 'if'
   21 |                 else
      |                 ^~~~
foo.c:5:29: warning: unused variable 't' [-Wunused-variable]
    5 |      int a, b, n, k = 0, i, t = 0;
      |                             ^

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