View Compilation Error

1_714_200_2670.cpp: In function 'int main()':
1_714_200_2670.cpp:26:26: error: 'a' was not declared in this scope
             printf("%d ",a[b[i]].r);
                          ^
1_714_200_2670.cpp:27:23: error: 'a' was not declared in this scope
         printf("%d\n",a[b[i]].r);
                       ^