View Compilation Error

0_0_17634707_5033.cpp:3:11: error: '::main' must return 'int'
 void main()
           ^
0_0_17634707_5033.cpp: In function 'int main()':
0_0_17634707_5033.cpp:5:1: error: '_int64' was not declared in this scope
 _int64 a,b,c;
 ^
0_0_17634707_5033.cpp:6:22: error: 'a' was not declared in this scope
 while(cin>>std::hex>>a>>std::hex>>b)
                      ^
0_0_17634707_5033.cpp:6:35: error: 'b' was not declared in this scope
 while(cin>>std::hex>>a>>std::hex>>b)
                                   ^
0_0_17634707_5033.cpp:8:2: error: 'c' was not declared in this scope
  c=a+b;
  ^