foo.c: In function 'main':
foo.c:6:22: warning: variable 'nn' set but not used [-Wunused-but-set-variable]
  long long int n,m=0,nn;
                      ^~
foo.c:7:2: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%lld",&n);
  ^~~~~~~~~~~~~~~~

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