likelihood<-function(thetast,fobs,merge2)
{
   fobss=fobs; thetss=thetast; merge22=merge2
    fst <- gn(thetass,merge22)
    if(min(fst)<=0){return(lik<-4)}
    lik <- sum(fobss * log(fobss/fst))
    lik
}