View Compilation Error

0_0_35965199_14951.cpp:4:10: error: 'n' was not declared in this scope
 string a[n];
          ^
0_0_35965199_14951.cpp: In function 'int main()':
0_0_35965199_14951.cpp:21:8: error: 'a' was not declared in this scope
   cin>>a[0];
        ^