View Compilation Error

0_0_39663329_13722.cpp: In function 'int main()':
0_0_39663329_13722.cpp:20:53: error: 'struct Node' has no member named 'i'
   20 |         while(~scanf("%d%d",&a[n].w ,&a[n].v)) a[n].i = n++;
      |                                                     ^