import sys

data = sys.stdin.read().split()
a, b = data[0], data[1]
n = len(a)
st = a + "#" + b + b
total_len = len(st)
z = [0] * total_len
l, r = 0, 0
ans = -1
for i in range(1, total_len):
    if i <= r:
        z[i] = min(r - i + 1, z[i - l])
    while i + z[i] < total_len and st[z[i]] == st[i + z[i]]:
        z[i] += 1
    if i + z[i] - 1 > r:
        l = i
        r = i + z[i] - 1
    if n + 1 <= i < 2 * n + 1:
        if z[i] == n:
            ans = i - (n + 1)
            break
print(ans)