#!/usr/bin/env python3

n, s, d = int(input()), 0, {}

for _ in range(n):
    c, t, x = input().split()
    if c not in d: d[c] = {'any': 0, 'left': 0, 'right': 0}
    d[c][t] = int(x)
    s += int(x)

def f(a, l, r): return max(l, r, min(a, 1))

ans = 1+sum(f(v['any'], v['left'], v['right']) for v in d.values())
print(ans if ans <= s else 'impossible')