View Compilation Error

0_0_31524457_31199.cpp: In function 'int main()':
0_0_31524457_31199.cpp:39:14: error: 'a' was not declared in this scope
   d=sqrt(pow(a.x-b.x,2)+pow(a.y-b.y,2));
              ^
0_0_31524457_31199.cpp:39:18: error: 'b' was not declared in this scope
   d=sqrt(pow(a.x-b.x,2)+pow(a.y-b.y,2));
                  ^