View Compilation Error

0_0_30402263_3545.cpp: In function 'int main()':
0_0_30402263_3545.cpp:15:74: error: 'b' was not declared in this scope
   for(int i=0;i<n;++i){scanf("%lld",a+i);ans+=a[i];d[i]=k-(a[i])%k;}sort(b,b+n,cmp);
                                                                          ^