View Compilation Error

0_0_18630237_29887.cpp:49:6: error: 'maxn' was not declared in this scope
 } pi[maxn];
      ^
0_0_18630237_29887.cpp: In function 'void solve()':
0_0_18630237_29887.cpp:117:16: error: 'pi' was not declared in this scope
  cen = gravity(pi, nn);
                ^
0_0_18630237_29887.cpp: In function 'int main()':
0_0_18630237_29887.cpp:136:47: error: 'pi' was not declared in this scope
   for (int i = 0; i<nn; i++) scanf("%lf%lf", &pi[i].x, &pi[i].y);
                                               ^