View Compilation Error

0_0_22029784_2572.cpp: In function 'int main()':
0_0_22029784_2572.cpp:33:18: error: 'xf' was not declared in this scope
     sum[2]=xf(5,j);
                  ^
0_0_22029784_2572.cpp:58:10: error: 'a' was not declared in this scope
          a[count]=sum[0]*sum[1]*sum[2]*sum[3];
          ^
0_0_22029784_2572.cpp:72:7: error: 'a' was not declared in this scope
  sort(a,a+count);
       ^