How to get only fields of the same type from an object in Typescript?

Question

typescript

type A = {
    a: number
}
  
type B = {
    b: number
}
  
type C = {
    c: number
}
  
interface ABC extends A, B, C {
    abc: number
}  

const obj: ABC = {
    a: 1,
    b: 2,
    c: 3,
    abc: 4
}

const objA: A = obj

How to make objA have only "a" field?