#!/bin/python3

# assumes the .ctd has been run
# check if the initial team assignment is valid

import sys 

n, m = map(int, input().split())
edges = [list(map(int, input().split())) for _ in range(m)]
edgeset = set()
s = input()
for e in edges:
    u = e[0]-1
    v = e[1]-1
    if (u, v) in edgeset or (v, u) in edgeset:
        sys.exit(43)
    edgeset.add((u, v))
    if s[u] == s[v]:
        sys.exit(43)
sys.exit(42)