foo.c: In function 'main':
foo.c:6:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d%d%d",&a,&b,&c);
     ^~~~~~~~~~~~~~~~~~~~~~~~
foo.c:7:18: warning: 'sum3' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int i,sum1,sum2,sum3,sum;
                  ^~~~
foo.c:7:13: warning: 'sum2' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int i,sum1,sum2,sum3,sum;
             ^~~~

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