#split the unsorted arrays into the 3 sub arrays which are sorted (i*3,i*3+1,i*3+2)
for (i to (round(n/3)+1))

    #checking for going outside the array size
    if (i*3 < n)
        B[i] <-A[i*3]
    endif

    if (i*3+1 < n)
    C[i] <- A[i*3+1]
    endif

    if (i*3+2 < n)
    D[i] <- A[i*3+2]
    endif

endfor

a,b,c,d <- 0;
#merge method but modified for 3 arrays, works until one array gets used up
while ( b<=Blength AND c<=Clength AND d<=Dlength )
        if (B[b]<=C[c] AND B[b]<=D[d]){
            A[a] <- B[b]
            b <- b + 1
        else if (C[c]<=B[b] AND C[c]<=D[d]){
            A[a] <- C[C]
            c <- c + 1
        else
            A[a] <- D[d]
            d <- d + 1
        endif
        a <- a + 1
endwhile

#one array got used so now we can use the normal Merge method, just need to check which array got used so we know which ones to use

if (b>Blength)

    while ( c<=Clength AND d<=Dlength )
        if (C[c]<D[d]){
            A[a] <- C[c]
            c <- c + 1
        else
            A[a] <- D[d]
            d <- d + 1
        endif
        a <- a + 1
    endwhile

else if (c>Clength)

    while ( b<=Blength AND d<=Dlength )
        if (B[b]<D[d]){
            A[a] <- B[b]
            b <- b + 1
        else
            A[a] <- D[d]
            d <- d + 1
        endif
        a <- a + 1
    endwhile

else

    while ( b<=Blength AND c<=Clength )
        if (B[b]<C[c]){
            A[a] <- B[b]
            b <- b + 1
        else
            A[a] <- C[c]
            c <- c + 1
        endif
        a <- a + 1
    endwhile

endif

#now just need to fill the final array with the left array that there are some elements left

while (b<Blength)

    A[a] <- B[b]
    b <- b + 1
    a <- a + 1
endwhile

while (c<Clength)

    A[a] <- C[c]
    c <- c + 1
    a <- a + 1
endwhile

while (d<Dlength)

    A[a] <- D[d]
    d <- d + 1
    a <- a + 1
endwhile