n = int(input())
drops = input()
picks = input()
cases = []
dropc = drops.count('C')
dropm = drops.count('M')
for i in range(6):
    cases.append([])
picksc = 0
picksm = 0
for i in range(n):
    pick = picks[i]
    if picks[i] == 'C':
        picksc += 1
        if picksc > dropc:
            pick = '-'
    elif picks[i] == 'M':
        picksm += 1
        if picksm > dropm:
            pick = '-'
    if drops[i] == '-':
        if pick == 'M':
            cases[4].append(i+1)
        elif pick == 'C':
            cases[5].append(i+1)
    elif drops[i] == 'C':
        if pick == 'M':
            cases[3].append(i+1)
        elif pick == '-':
            cases[0].append(i+1)
    elif drops[i] == 'M':
        if pick == 'C':
            cases[2].append(i+1)
        elif pick == '-':
            cases[1].append(i+1)
cnts = [len(c) for c in cases]
paths = []
#first cut off one of the MC or CM cases by a big cycle
if cnts[2] < cnts[3]:
    # must have a M- and -C to be solvable
    path = []
    path.append(5)
    cnts[5] -= 1
    c = cnts[2]
    for i in range(c):
        path.append(3)
        cnts[3] -= 1
        path.append(2)
        cnts[2] -= 1
    path.append(3)
    cnts[3] -= 1
    path.append(1)
    cnts[1] -= 1
    paths.append(path)
    # solve remaining CM if theyre there
    rm = cnts[3]
    for i in range(rm):
        paths.append([5, 3, 1])
        cnts[5] -= 1
        cnts[3] -= 1
        cnts[1] -= 1
elif cnts[2] > 0 and cnts[2] == cnts[3]:
    #check if we use -C C- or -M M-
    path = []
    if cnts[5] > 0:
        path.append(5)
        cnts[5] -= 1
        rm = cnts[2]
        for i in range(rm):
            path.append(3)
            cnts[3] -= 1
            path.append(2)
            cnts[2] -= 1
        path.append(0)
        cnts[0] -= 1
    else:
        path.append(4)
        cnts[4] -= 1
        rm = cnts[2]
        for i in range(rm):
            path.append(2)
            cnts[2] -= 1
            path.append(3)
            cnts[3] -= 1
        path.append(1)
        cnts[1] -= 1
    paths.append(path)
elif cnts[2] > cnts[3]:
    #must have a C- and -M to be solvable
    path = []
    path.append(4)
    cnts[4] -= 1
    c = cnts[3]
    for i in range(c):
        path.append(2)
        cnts[2] -= 1
        path.append(3)
        cnts[3] -= 1
    path.append(2)
    cnts[2] -= 1
    path.append(0)
    cnts[0] -= 1
    paths.append(path)
    #solve remaining MC if theyre there
    rm = cnts[2]
    for i in range(rm):
        paths.append([4,2,0])
        cnts[4] -= 1
        cnts[2] -= 1
        cnts[0] -= 1
#solve remaining -C C- and -M M- combos
rm = cnts[0]
for i in range(rm):
    paths.append([5,0])
    cnts[5] -= 1
    cnts[0] -= 1
rm = cnts[1]
for i in range(rm):
    paths.append([4,1])
    cnts[4] -= 1
    cnts[1] -= 1
#output the actual route
ixs = [0] * 6
if len(paths) == 0:
    print(0)
else:
    res = ""
    lenres = 0
    for path in paths:
        for ix in range(len(path)):
            cs = path[ix]
            loc = cases[cs][ixs[cs]]
            ixs[cs] += 1
            res += "DRIVE " + str(loc) + "\n"
            lenres += 1
            if ix == 0:
                res += "PICKUP\n"
                lenres += 1
            elif ix == len(path) - 1:
                res += "DROPOFF\n"
                lenres += 1
            else:
                res += "DROPOFF\nPICKUP\n"
                lenres += 2
    print(lenres)
    print(res, end = '')