View Compilation Error

0_0_23670552_19188.cpp: In function 'int main()':
0_0_23670552_19188.cpp:40:53: error: 'a' was not declared in this scope
         for(int i = 1; i <= n; i++) scanf("%lf%lf",&a[i].x,&a[i].y);
                                                     ^