MOD = 10**9 + 7

A = int(input())
B_str = input().strip()

D = len(B_str)

# Convert B from base A to MOD
B_mod = 0
for c in B_str:
    B_mod = (B_mod * A + int(c)) % MOD

m_max = D - 1

sum_part1 = 0
if D >= 2:
    n = D - 2
    A_val = A
    pow_A_n = pow(A_val, n, MOD)
    term1 = ((n + 1) * pow_A_n) % MOD
    term2 = (n * pow_A_n * A_val) % MOD
    numer = (1 - term1 + term2) % MOD
    numer = (numer + MOD) % MOD  # Ensure non-negative
    inv_Am1 = pow((A_val - 1) % MOD, MOD - 2, MOD)
    sum_part1 = (A_val * numer) % MOD
    sum_part1 = (sum_part1 * inv_Am1) % MOD

sum_part2 = 0
if D >= 1:
    A_pow = pow(A, m_max, MOD)
    term = (B_mod - A_pow + 1) % MOD
    term = (term + MOD) % MOD  # Ensure non-negative
    sum_part2 = (m_max * term) % MOD

total = (sum_part1 + sum_part2) % MOD
print(total)