foo.c:2:1: warning: return type defaults to 'int' [-Wimplicit-int]
    2 | main(){
      | ^~~~
foo.c: In function 'main':
foo.c:9:9: warning: 'sum' may be used uninitialized in this function [-Wmaybe-uninitialized]
    9 |         printf("%d",sum);
      |         ^~~~~~~~~~~~~~~~

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