import sys

# sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
def SI(): return sys.stdin.readline().rstrip()
dij = [(0, 1), (-1, 0), (0, -1), (1, 0)]
# dij = [(0, 1), (-1, 0), (0, -1), (1, 0), (1, 1), (1, -1), (-1, 1), (-1, -1)]
inf = 10**16
# md = 998244353
md = 10**9+7

a = II()
bb = list(map(int, SI()))
# print(b)
n = len(bb)

n2 = n-2
ans = a*(n2*pow(a, n2+1, md)-(n2+1)*pow(a, n2, md)+1)*pow(a-1, md-2, md)%md
bb[0] -= 1
bb[-1] += 1
cnt = 0
base = 1
for b in bb[::-1]:
    cnt += base*b
    cnt %= md
    base = base*a%md
ans += cnt*(n-1)
print(ans%md)