IF statement causing wrong results in function

I am trying work on a coursera assignment in R. My code works correctly for assignment 1 where I write a function in R to rank Hospitals; in assignment 2 I have to add few IF or IF ELSE IF statements to the function already written.

Function gives a final dataframe.

1. IF input argument num==best, function returns the first row of final data frame
2. IF input argument num==worst, function returns the last row of final data frame
3. If input argument num > max row count of final data frame, function returns NA
4. If input argument num< max row count, function returns that row from data frame

Now, the if statement are working correctly for only scenario 3 and 4. For 1 and 2 scenarios, it is returning NA- which is the return value of scenario 3.

There is something wrong with the way I am writing IF statements ( can be sequence or the condition or something else) because of which I am getting NA return value for scenario 1,2

Code below, TIA

outcomeDF<-outcome[,c(2,7,n)]
names(outcomeDF)<-c("Hospital","State","Outcomess")
finalDF<-filter(outcomeDF,outcomeDF$State==sta)
     
DFSlist<-arrange(finalDF,finalDF$State,finalDF$Outcomess,finalDF$Hospital)

if (num > nrow(DFSlist)) print ("NA")
  else if (num < nrow(DFSlist)) c<-(DFSlist[num,])
  else if (num =="best")c<-(DFSlist[1,])
  else (num =="worst")c<-(DFSlist[(nrow(DFSlist)),])
return(c)