def test_rewind_randint():
writeint(r())
checkpoint()
writeint(r())
rewind()
writeint(r())
v = readints()
assert len(v) == 4
assert v[0] != v[1]
assert v[1] == v[2]
assert v[2] != v[3]
assert v[0] != v[2]
assert v[1] != v[3]
assert v[0] != v[1]
from rew import rewind, checkpoint
from sys import stdin
loc = dict()
glob = dict()
while True:
checkpoint()
print(loc)
print(">>>", end="", flush=True)
snippet = stdin.readline().strip()
if snippet == "":
rewind(-1)
break
if snippet == "undo":
rewind()
else:
try:
exec(snippet, glob, loc)
except Exception as e:
print(e)