View Compilation Error

0_0_31803645_9665.cpp: In function 'int main()':
0_0_31803645_9665.cpp:16:23: error: ISO C++ forbids comparison between pointer and integer [-fpermissive]
         for(int i=0;i<a;i++)
                       ^
0_0_31803645_9665.cpp:18:25: error: 'b' was not declared in this scope
             scanf("%d",&b);
                         ^
0_0_31803645_9665.cpp:20:26: error: invalid operands of types 'int [200010]' and 'int' to binary 'operator/'
             if(vis[b]==a/2)
                          ^
0_0_31803645_9665.cpp:22:17: error: 'c' was not declared in this scope
                 c=b;
                 ^
0_0_31803645_9665.cpp:25:23: error: 'c' was not declared in this scope
         printf("%d\n",c);
                       ^