# mod = 10**9 + 7しないと落ちる

n, m = map(int, input().split())
assert 2 <= n <= 10**5
assert 0 <= m <= 10**5

s = input()
assert len(s) == n
assert all(c in 'PCDA' for c in s)

graph = [[] for i in range(n)]
for _ in range(m):
    u, v = map(int, input().split())
    assert 1 <= u < v <= n
    graph[u - 1].append(v - 1)
    graph[v - 1].append(u - 1)


nodes = {c: [] for c in 'PDCA'}
pre = {
    'D': 'P',
    'C': 'D',
    'A': 'C',
}
for i in range(n):
    nodes[s[i]].append(i)


cnt = [1 if s[i] == 'P' else 0 for i in range(n)]
for c in 'DCA':
    for v in nodes[c]:
        for u in graph[v]:
            if s[u] == pre[c]:
                cnt[v] += cnt[u]
print(sum([cnt[v] for v in nodes['A']]))