View Compilation Error

0_0_16682922_6595.cpp: In function 'int main()':
0_0_16682922_6595.cpp:11:12: error: expected primary-expression before ']' token
   char a[s[]];
            ^
0_0_16682922_6595.cpp:13:15: error: 'a' was not declared in this scope
   for(int j=0;a[j]!='\0';j++)
               ^