View Compilation Error

0_0_37379035_23031.cpp:7:10: error: expected initializer before 'a'
  string  a[10000];
          ^
0_0_37379035_23031.cpp: In function 'int main()':
0_0_37379035_23031.cpp:25:20: error: 'a' was not declared in this scope
     scanf("%d %d",&a[i].v,&a[i].w);
                    ^
0_0_37379035_23031.cpp:29:9: error: 'a' was not declared in this scope
   sort (a,a+n,cmp);
         ^