foo.c:1:1: warning: return type defaults to 'int' [-Wimplicit-int]
    1 | main(){printf("80");}
      | ^~~~
foo.c: In function 'main':
foo.c:1:8: warning: implicit declaration of function 'printf' [-Wimplicit-function-declaration]
    1 | main(){printf("80");}
      |        ^~~~~~
foo.c:1:8: warning: incompatible implicit declaration of built-in function 'printf'
foo.c:1:1: note: include '<stdio.h>' or provide a declaration of 'printf'
  +++ |+#include <stdio.h>
    1 | main(){printf("80");}

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