sygxoneysi <- function(akolouthia,v1,v2,v3){
  n1 <- v2-v1+1
  n2 <- v3-v2
  aristera <- c(1)
  for (i in c(1:n1)){
    aristera[i] <- akolouthia[v1+i-1]
  }
  aristera[n1+1] <- Inf
  dexia <- c(1)
  for (i in c(1:n2)){
    dexia[i] <- akolouthia[v2+i]
  }
  dexia[n2+1] <- Inf
  i <- 1
  j <- 1
  for (k in c(v1:v3)){
    if (anisosi(aristera[i],dexia[j])) {
      akolouthia[k] <- aristera[i]
      i <- i+1
    }
    else {
      akolouthia[k] <- dexia[j]
      j <- j+1
    }
  }
  akolouthia
}

ttt <- c(4,6, 2,5,7,9, 3,4,7,12,21, 6,5,0)
ttt2 <- c(4,6, 2,5,7,9,10, 3,4,7,12,21, 6,5,0)
sygxoneysi(ttt,3,6,11)
sygxoneysi(ttt2,3,7,11)