View Compilation Error

0_0_24884136_17288.cpp: In function 'int main()':
0_0_24884136_17288.cpp:28:22: error: 'a' was not declared in this scope
                 for(;a[k]==a[j];k++,j++)
                      ^
0_0_24884136_17288.cpp:30:20: error: 'a' was not declared in this scope
                 if(a[k]<a[j])
                    ^