How to write rewrite in Kubernetes?

Question

Kubernetes

You need to rewrite:
1. a-service/a -> a-service/a
2. b-service/b -> b-service/b
how to describe it correctly in Ingress?
So it does not work, how to do the redirect correctly?

{
              "path": "a-service/a", 
              "backend": {
                "serviceName": "a-service/a",
                "servicePort": 80
              }
            },
            {
              "path": "b-service/b", 
              "backend": {
                "serviceName": "b-service/b",
                "servicePort": 80
              }
            },