foo.c:7:6: warning: return type of 'main' is not 'int' [-Wmain]
 void main(){
      ^~~~
foo.c: In function 'main':
foo.c:9:1: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
 scanf("%d",&n);
 ^~~~~~~~~~~~~~

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