View Compilation Error

0_0_28150753_15980.cpp: In function 'int main()':
0_0_28150753_15980.cpp:9:18: error: 'a' was not declared in this scope
  scanf("%d%d",&n,a+1);
                  ^
0_0_28150753_15980.cpp:10:15: error: 'i' was not declared in this scope
  op=ed=1; s=a[i]; tp=0;
               ^