View Compilation Error

0_0_27196933_21832.cpp: In function 'int judge(double)':
0_0_27196933_21832.cpp:12:42: error: 'pi' was not declared in this scope
             sum+=(int)(1.0*str[i]*str[i]*pi/mid);
                                          ^
0_0_27196933_21832.cpp: In function 'int main()':
0_0_27196933_21832.cpp:28:38: error: 'pi' was not declared in this scope
               sum+=1.0*str[i]*str[i]*pi;
                                      ^
0_0_27196933_21832.cpp:32:29: error: invalid operands of types 'double' and 'double(double)' to binary 'operator>='
           while(right-left>=exp)
                             ^