import sys

sys.setrecursionlimit(200005)
int1 = lambda x: int(x)-1
pDB = lambda *x: print(*x, end="\n", file=sys.stderr)
p2D = lambda x: print(*x, sep="\n", end="\n\n", file=sys.stderr)
def II(): return int(sys.stdin.readline())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def LI1(): return list(map(int1, sys.stdin.readline().split()))
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 = (1 << 63)-1
# inf = (1 << 31)-1
# md = 10**9+7
md = 998244353

import typing

def inv_gcd(a, b):
    a %= b
    if a == 0: return b, 0
    s, t = b, a
    m0, m1 = 0, 1
    while t:
        u = s//t
        s -= t*u
        m0 -= m1*u
        s, t = t, s
        m0, m1 = m1, m0
    if m0 < 0: m0 += b//s
    return s, m0

# 複数の「mで割ったらr余る」という条件を満たすxをmod zで返す
# 返り値 x,z（解なしの場合は0,0）
def crt(r: typing.List[int], m: typing.List[int]) -> typing.Tuple[int, int]:
    assert len(r) == len(m)

    n = len(r)
    r0, m0 = 0, 1
    for i in range(n):
        assert 1 <= m[i]
        r1 = r[i]%m[i]
        m1 = m[i]
        if m0 < m1:
            r0, r1 = r1, r0
            m0, m1 = m1, m0
        if m0%m1 == 0:
            if r0%m1 != r1: return 0, 0
            continue

        g, im = inv_gcd(m0, m1)

        u1 = m1//g
        if (r1-r0)%g: return 0, 0

        x = (r1-r0)//g%u1*im%u1

        r0 += x*m0
        m0 *= u1
        if r0 < 0: r0 += m0
        if r0 > N: return 0, 0

    return r0, m0

N = II()
m = II()
bb, cc = [], []
for _ in range(m):
    b, c = LI()
    if b == 1: continue
    c %= b
    bb.append(b)
    cc.append(c)

x, z = crt(cc, bb)
# print(x,z)

if z == 0 or x > N:
    print("NaN")
else:
    print(x)