foo.c: In function 'main':
foo.c:13:9: warning: 'f3' may be used uninitialized [-Wmaybe-uninitialized]
   13 |         printf("%d",f3);
      |         ^~~~~~~~~~~~~~~
foo.c:5:13: note: 'f3' was declared here
    5 |         int f3;
      |             ^~

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