#!/usr/bin/python3
import sys
import collections

d = collections.defaultdict(lambda: [0,0,0])
mappy = {'any': 0, 'left': 1, 'right': 2}
n = (int)(sys.stdin.readline())
taken = 0

for _ in range(0,n):
    typ, fit, count = sys.stdin.readline().strip().split()
    d[typ][mappy[fit]] = (int)(count)

for v in d.values():
    if v[1] > 0 and v[1] >= v[2]:
        taken += v[1]
    elif v[2] > 0 and v[2] > v[1]:
        taken += v[2]
    elif v[0] > 0:
        taken += 1

if taken == sum([sum(v) for v in d.values()]):
    print('impossible')
else:
    print(taken+1)