/in/foo.cc:3:12: error: array bound is not an integer constant before ']' token
 int n,a[n+1],sum1,sum2;
            ^
/in/foo.cc: In function 'int main()':
/in/foo.cc:8:8: error: 'a' was not declared in this scope
   cin>>a[i];
        ^
/in/foo.cc:14:8: error: 'a' was not declared in this scope
   cin>>a[i];
        ^