View Compilation Error

0_0_17521102_23894.cpp: In function 'int main()':
0_0_17521102_23894.cpp:6:1: error: expected initializer before 'while'
 while(scanf("%lf",&r)!=EOF)
 ^
0_0_17521102_23894.cpp:8:4: error: 'else' without a previous 'if'
    else
    ^
0_0_17521102_23894.cpp:9:25: error: 'r' was not declared in this scope
    printf("%.3f\n",4*PI*r*r*r/3.0);
                         ^