def modinv(a, MOD):
    b = MOD
    u = 1
    v = 0
    while b:
        t = a // b
        a -= t * b
        u -= t * v
        a, b = b, a
        u, v = v, u
    u %= MOD
    return u

def Garner(M, R):
    m_prod = M[0]
    C = R[0]
    for m, r in zip(M[1:], R[1:]):
        t = (r - C) * modinv(m_prod, m) % m
        C += t * m_prod
        m_prod *= m
    
    return C

from math import gcd

def isprime(n):
    if n <= 1:
        return False
    elif n == 2:
        return True
    elif n % 2 == 0:
        return False
    
    A = [2, 325, 9375, 28178, 450775, 9780504, 1795265022]
    s = 0
    d = n - 1
    while d % 2 == 0:
        s += 1
        d >>= 1
    
    for a in A:
        if a % n == 0:
            return True
        x = pow(a, d, n)
        if x != 1:
            for t in range(s):
                if x == n - 1:
                    break
                x = x * x % n
            else:
                return False
    return True
        
def pollard(n):
    if n % 2 == 0:
        return 2
    if isprime(n):
        return n
    
    f = lambda x:(x * x + 1) % n
    
    step = 0
    while 1:
        step += 1
        x = step
        y = f(x)
        while 1:
            p = gcd(y - x + n, n)
            if p == 0 or p == n:
                break
            if p != 1:
                return p
            x = f(x)
            y = f(f(y))

def primefact(n):
    if n == 1:
        return []
    p = pollard(n)
    if p == n:
        return [p]
    left = primefact(p)
    right = primefact(n // p)
    left += right
    return sorted(left)

n = int(input())
m = int(input())
mr = []
for _ in range(m):
    b, c = map(int, input().split())
    mr.append((b, c % b))

mm = {}
rr = {}
ng = False
for m, r in mr:
    if m == 1:
        continue
    
    primes = primefact(m)
    bef = -1
    x = 1
    for p in primes:
        if p != bef:
            if bef != -1:
                if bef in mm:
                    r_ = r % x
                    if mm[bef] >= x:
                        if rr[bef] % x != r_:
                            ng = True
                            break
                    else:
                        if r_ % mm[bef] != rr[bef]:
                            ng = True
                            break
                        mm[bef] = x
                        rr[bef] = r_

                else:
                    mm[bef] = x
                    rr[bef] = r % x
            x = p
            bef = p
        else:
            x *= p

    if bef in mm:
        r_ = r % x
        if mm[bef] >= x:
            if rr[bef] % x != r_:
                ng = True
        else:
            if r_ % mm[bef] != rr[bef]:
                ng = True                    
            mm[bef] = x
            rr[bef] = r_
    else:
        mm[bef] = x
        rr[bef] = r % x

    if ng:
        break
if ng:
    print("NaN")
else:
    M = [1]
    R = [0]
    for k in mm:
        M.append(mm[k])
        R.append(rr[k])
    ans = Garner(M, R)
    if ans <= n:
        print(ans)
    else:
        print("NaN")