N=int(input())
M=int(input())
X=[]
Y=[]
for i in range(M):
  b,c=map(int,input().split())
  X.append(c%b)
  Y.append(b)
def inv_gcd(a, b):
    a %= b
    if a == 0: return b, 0
    s = b
    t = a
    m0 = 0
    m1 = 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

def inv_mod(x, m):
    assert 1 <= m
    g, im = inv_gcd(x, m)
    assert g == 1
    return im

def crt(r, m):
    assert len(r) == len(m)
    n = len(r)
    r0 = 0
    m0 = 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 * im % u1
        r0 += x * m0
        m0 *= u1
        if (r0 < 0): r0 += m0
        if r0>N:return 0,0
    return r0, m0

ANS=crt(X,Y)
if ANS[1]==0:
  print('NaN')
else:
  print(ANS[0])