09:34:07:493 USER_DEBUG [63]|DEBUG|Response for Payload : [{"errorCode":"URL_NOT_RESET","message":"Destination URL not reset. The URL returned from login must be set"}]

public class OAuth2
{

    public String id{get;set;}
    public String issued_at{get;set;}
    public String instance_url{get;set;}
    public String signature{get;set;}
    public String access_token{get;set;}

}

RESTCreds__c r = RESTCreds__c.getValues('1');

String clientId = r.ConsumerKey__c;
String clientSecret = r.ConsumerSecret__c;
String userName = r.Username__c;
String password = r.Password__c;
String url = r.URL__c;
System.debug(clientId);
System.debug(clientSecret);
System.debug(userName);
System.debug(password);
System.debug(url);

String reqbody = 'grant_type=password&client_id='+clientId+'&client_secret='+clientSecret+'&username='+username+'&password='+password;

HTTP h = new HTTP();
HttpRequest req = new HttpRequest();
req.setBody(reqbody);
req.setMethod('POST');
req.setEndPoint(url);

HttpResponse res = h.send(req);
System.debug('Response : '+res);
System.debug('Response Body : '+res.getBody());

OAuth2 objAuthenticationInfo = (OAuth2) JSON.deserialize(res.getBody(),OAuth2.class);
System.debug(objAuthenticationInfo);
System.debug('Id = '+objAuthenticationInfo.id);
System.debug('Issued At = '+objAuthenticationInfo.issued_at);
System.debug(' Instance URL = '+objAuthenticationInfo.instance_url);
System.debug(' Signature = '+objAuthenticationInfo.signature);
System.debug(' Access Token = '+objAuthenticationinfo.access_token);




String jsonstr = '{"nam":"Test 1"}';
System.debug(jsonstr);


if(objAuthenticationInfo.access_token != null)
{
    Http h1 = new Http();
    HttpRequest req1 = new HttpRequest();
    req1.setHeader('Authorization','Bearer '+objAuthenticationInfo.access_token);
    req1.setHeader('Content-Type','application/json');
    req1.setHeader('accept','application/json');
    req1.setBody(jsonstr);
    req1.setMethod('POST');
    req1.setEndpoint('https://login.salesforce.com/services/apexrest/Account');
    HttpResponse res1 = h1.send(req1);
    System.debug('Response for Payload : '+res1.getBody());


}