View Compilation Error

0_0_17575008_13847.cpp: In function 'int main()':
0_0_17575008_13847.cpp:11:6: error: 'ans' was not declared in this scope
  {.0-ans*1.0/((n*(n-1)*(n-2))/6));
      ^
0_0_17575008_13847.cpp:22:2: error: expected ')' before 'return'
  return 0;
  ^