View Compilation Error

0_0_33986577_10443.cpp:16:2: error: 'a' does not name a type
  a,b;
  ^
0_0_33986577_10443.cpp: In function 'int main()':
0_0_33986577_10443.cpp:50:9: error: 'struct node' has no member named 'a'
    a[i].a=x;
         ^
0_0_33986577_10443.cpp:51:9: error: 'struct node' has no member named 'b'
    a[i].b=y;
         ^