View Compilation Error

0_0_33159893_3585.cpp: In function 'double rotate_caliper(Polyon)':
0_0_33159893_3585.cpp:302:38: error: 'a' was not declared in this scope
   while(area_2(p[i],p[(i+1)%n],p[j])<a
                                      ^
0_0_33159893_3585.cpp:302:38: error: expected ')' at end of input
0_0_33159893_3585.cpp:302:38: error: expected statement at end of input
0_0_33159893_3585.cpp:302:38: error: expected '}' at end of input
0_0_33159893_3585.cpp:302:38: error: expected '}' at end of input