Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [N] * N
  Q[0] = [DD[-1][1] - 1]
  for i in range(N):
    s = Q[i]
    if s == N:
      break
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q.append(adj)
  if sum(dist) == DD[-1][0]:
    for e in E:
      print(e[0], e[1])
  else:
    print(-1)

Fixed submission:
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1] + [N] * N
  tail = 1
  for i in range(N):
    s = Q[i]
    if s == N:
      print(-1)
      break
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q[tail] = adj
        tail += 1
  else:
    if sum(dist) == DD[-1][0]:
      for e in E:
        print(e[0], e[1])
    else:
      print(-1)

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1]
  for i in range(N - 1):
    s = Q[i]
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q.append(adj)
  if sum(dist) == DD[-1][0]:
    for e in E:
      print(e[0], e[1])
  else:
    print(-1)

Fixed submission:
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1] + [N] * N
  tail = 1
  for i in range(N):
    s = Q[i]
    if s == N:
      print(-1)
      break
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q[tail] = adj
        tail += 1
  else:
    if sum(dist) == DD[-1][0]:
      for e in E:
        print(e[0], e[1])
    else:
      print(-1)

Buggy python submission (verdict: Runtime Error):
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1]
  for i in range(N):
    s = Q[i]
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q.append(adj)
  if sum(dist) == DD[-1][0]:
    for e in E:
      print(e[0], e[1])
  else:
    print(-1)

Fixed submission:
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1] + [N] * N
  tail = 1
  for i in range(N):
    s = Q[i]
    if s == N:
      print(-1)
      break
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q[tail] = adj
        tail += 1
  else:
    if sum(dist) == DD[-1][0]:
      for e in E:
        print(e[0], e[1])
    else:
      print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1]
  while Q:
    s = Q[0]
    Q = Q[1:]
    for adj in Adj[s]:
      if dist[s] + 1 < dist[adj]:
        dist[adj] = dist[s] + 1
        Q.append(adj)
  if sum(dist) == DD[-1][0]:
    for e in E:
      print(e[0], e[1])
  else:
    print(-1)

Fixed submission:
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1] + [N] * N
  tail = 1
  for i in range(N):
    s = Q[i]
    if s == N:
      print(-1)
      break
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q[tail] = adj
        tail += 1
  else:
    if sum(dist) == DD[-1][0]:
      for e in E:
        print(e[0], e[1])
    else:
      print(-1)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1]
  while Q:
    s = Q[0]
    Q = Q[1:]
    for adj in Adj[s]:
      if dist[s] + 1 < dist[adj]:
        dist[adj] = dist[s] + 1
        Q.append(adj)
  if sum(dist) == DD[-1][0]:
    for e in E:
      print(e[0], e[1])
  else:
    print(-1)

Fixed submission:
from collections import defaultdict
N = int(input())
C = defaultdict(int)
for i in range(N):
  D = int(input())
  C[D] = i + 1
E = []
H = [1] * (N + 1)
DD = sorted([[k, v] for k, v in C.items()], reverse=True)
Adj = [[] for i in range(N)]
for D, n in DD[:-1]:
  try:
    p = C[D - N + 2 * H[n]]
    if n == p:
      raise Error
    E.append([n, p])
    Adj[n - 1].append(p - 1)
    Adj[p - 1].append(n - 1)
    H[p] += H[n]
  except:
    print(-1)
    break
else:
  dist = [N] * N
  dist[DD[-1][1] - 1] = 0
  Q = [DD[-1][1] - 1] + [N] * N
  tail = 1
  for i in range(N):
    s = Q[i]
    if s == N:
      print(-1)
      break
    for adj in Adj[s]:
      if dist[adj] == N:
        dist[adj] = dist[s] + 1
        Q[tail] = adj
        tail += 1
  else:
    if sum(dist) == DD[-1][0]:
      for e in E:
        print(e[0], e[1])
    else:
      print(-1)