View Compilation Error

0_0_35249550_7777.cpp: In function 'int main()':
0_0_35249550_7777.cpp:4:22: error: expected ')' before ';' token
 #define PI acos(-1.0);//为追求高精度，使用反余弦函数acos，因为cosπ=-1，故：acos(-1)=π
                      ^
0_0_35249550_7777.cpp:30:38: note: in expansion of macro 'PI'
                 num+=(int)(a[i]*a[i]*PI/mid);
                                      ^
0_0_35249550_7777.cpp:30:40: error: expected primary-expression before '/' token
                 num+=(int)(a[i]*a[i]*PI/mid);
                                        ^