View Compilation Error

0_0_19620735_32584.cpp:4:11: error: '::main' must return 'int'
 void main()
           ^
0_0_19620735_32584.cpp: In function 'int main()':
0_0_19620735_32584.cpp:13:19: error: 'strlen' was not declared in this scope
   int len=strlen(s);
                   ^
0_0_19620735_32584.cpp:28:6: error: 'j' was not declared in this scope
   if(j==len)
      ^