#!/usr/bin/python3

n = int(input())

drawer = {}
to_idx = {"left": 0, "right" : 1, "any" : 2}

for _ in range(n):
    i, j, k = input().split()
    k = int(k)
    if i not in drawer:
        drawer[i] = [0, 0, 0]
    drawer[i][to_idx[j]] += k

if all(sum(drawer[key]) < 2 or drawer[key][0] + drawer[key][2] == 0 or 
        drawer[key][1] + drawer[key][2] == 0 for key in drawer):
    print("impossible")
else:
    print(sum(max(drawer[key][0], drawer[key][1], 1) for key in drawer) + 1)