View Compilation Error

0_0_34161378_28517.cpp: In function 'int main()':
0_0_34161378_28517.cpp:10:3: error: expected unqualified-id before 'double'
   double flag=0;
   ^
0_0_34161378_28517.cpp:17:5: error: 'flag' was not declared in this scope
     flag++;
     ^
0_0_34161378_28517.cpp:20:31: error: 'flag' was not declared in this scope
   printf("%.5lf\n", 1.00000 / flag);
                               ^