foo.c: In function 'main':
foo.c:5:24: warning: unused variable 'z' [-Wunused-variable]
   int n,c=0,s=0,flag=1,z;
                        ^
foo.c:5:17: warning: unused variable 'flag' [-Wunused-variable]
   int n,c=0,s=0,flag=1,z;
                 ^~~~
foo.c:8:5: warning: ignoring return value of 'scanf', declared with attribute warn_unused_result [-Wunused-result]
     scanf("%d",&y[n]);
     ^~~~~~~~~~~~~~~~~

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