View Compilation Error

0_0_23374309_787.cpp:3:6: error: expected constructor, destructor, or type conversion before '(' token
 scanf("%d %d",&a,&b);
      ^
0_0_23374309_787.cpp:4:7: error: expected constructor, destructor, or type conversion before '(' token
 printf("%d",a+b);
       ^
0_0_23374309_787.cpp:5:1: error: expected unqualified-id before 'return'
 return o;
 ^