import sys

line = sys.stdin.buffer.readline().split()
n, m = int(line[0]), int(line[1])
g = sys.stdin.buffer.readline().strip()
pi = [0] * n
for i in range(1, n):
    j = pi[i-1]
    while j > 0 and g[i] != g[j]:
        j = pi[j-1]
    if g[i] == g[j]: j += 1
    pi[i] = j
ans = 0
idx = 0
j = 0
while True:
    chunk = sys.stdin.buffer.read(131072)
    if not chunk:
        break
    chunk = chunk.replace(b'\n', b'').replace(b'\r', b'')
    for c in chunk:
        while j > 0 and c != g[j]:
            j = pi[j-1]
        if c == g[j]: 
            j += 1
        if j == n:
            ans += (idx - n + 1)
            j = pi[n-1]
        idx += 1
print(ans)