View Compilation Error

0_0_38588503_12415.cpp:2:11: error: '::main' must return 'int'
 void main(){
           ^
0_0_38588503_12415.cpp: In function 'int main()':
0_0_38588503_12415.cpp:14:9: error: 'f' was not declared in this scope
  e+=1.0/f(i);
         ^