View Compilation Error

0_0_27163503_16200.cpp:3:11: error: '::main' must return 'int'
 void main()
           ^
0_0_27163503_16200.cpp: In function 'int main()':
0_0_27163503_16200.cpp:8:3: error: 'c' was not declared in this scope
   c = 4*pai*a*a*a/3; 
   ^