View Compilation Error

0_0_19098647_15192.cpp: In function 'int main()':
0_0_19098647_15192.cpp:6:16: error: conflicting declaration 'long long int a [50]'
  long long a[50];
                ^
0_0_19098647_15192.cpp:5:8: note: previous declaration as 'int a'
  int n,a,b;
        ^
0_0_19098647_15192.cpp:10:6: error: invalid types 'int[int]' for array subscript
   a[1]=1;
      ^
0_0_19098647_15192.cpp:11:6: error: invalid types 'int[int]' for array subscript
   a[2]=2;
      ^
0_0_19098647_15192.cpp:13:7: error: invalid types 'int[int]' for array subscript
    a[i]=a[i-1]+a[i-2];
       ^
0_0_19098647_15192.cpp:13:14: error: invalid types 'int[int]' for array subscript
    a[i]=a[i-1]+a[i-2];
              ^
0_0_19098647_15192.cpp:13:21: error: invalid types 'int[int]' for array subscript
    a[i]=a[i-1]+a[i-2];
                     ^
0_0_19098647_15192.cpp:15:24: error: invalid types 'int[int]' for array subscript
   printf("%lld\n",a[b-a]);
                        ^