View Compilation Error

0_0_34385047_26467.cpp: In function 'int main()':
0_0_34385047_26467.cpp:5:2: error: expected initializer before 'scanf'
  scanf("%d",&n);
  ^
0_0_34385047_26467.cpp:7:3: error: 'a' was not declared in this scope
   a={'0'};
   ^
0_0_34385047_26467.cpp:10:26: error: 'strlen' was not declared in this scope
   for(int j=0;j<=strlen(a)/2+1;j++){
                          ^