View Compilation Error

0_0_32434674_9037.cpp:7:13: error: array bound is not an integer constant before ']' token
 double s[MAX];
             ^
0_0_32434674_9037.cpp: In function 'int main()':
0_0_32434674_9037.cpp:13:5: error: 's' was not declared in this scope
     s[1] = 1, s[2] = PI / 4.0;
     ^
0_0_32434674_9037.cpp:14:25: error: 'MAXN' was not declared in this scope
     for(int i = 3 ; i < MAXN ; i++)
                         ^
0_0_32434674_9037.cpp:21:34: error: 'si' was not declared in this scope
    printf("%.10lf\n",1.0*r/(n+1)/si[n]);
                                  ^
0_0_32434674_9037.cpp:23:35: error: 'si' was not declared in this scope
    printf("%.10lf\n",1.0*r/(n+1)/(si[n]*pi/2));
                                   ^
0_0_32434674_9037.cpp:23:41: error: 'pi' was not declared in this scope
    printf("%.10lf\n",1.0*r/(n+1)/(si[n]*pi/2));
                                         ^