from operator import itemgetter

n, m ,k = map(int, input().split())
orders = list(map(int, input().split()))
indexes = list(range(1, m+1))
indexes, orders = zip(*sorted(zip(indexes, orders), key=itemgetter(1)))
indexes, orders = list(indexes), list(orders)
chosen = []


for i in range(1, n+1):
    available = [j for j in orders if j >= i]
    aval_inds = indexes[:len(available)]
    for _ in range(k):
        if available:
            pick_idx = aval_inds[0]
            chosen.append((pick_idx, i))
            available = available[1:]
            orders = orders[1:]
            aval_inds = aval_inds[1:]
            indexes = indexes[1:]
    if orders:
        while orders[0] <= i:
            orders = orders[1:]
            indexes = indexes[1:]

print(len(chosen))
for i in chosen:
    print(i[0], i[1])