import math

N = int(input())
M = int(input())

congruences = []
for _ in range(M):
    B, C = map(int, input().split())
    c = C % B
    congruences.append((B, c))

if M == 0:
    print("NaN")
else:
    current_a, current_mod = congruences[0][1], congruences[0][0]
    has_solution = True

    for i in range(1, M):
        B_i, c_i = congruences[i]
        d = math.gcd(current_mod, B_i)
        if (c_i - current_a) % d != 0:
            has_solution = False
            break

        new_mod = (current_mod // d) * B_i
        a = current_mod // d
        b_mod = B_i // d
        rhs = (c_i - current_a) // d

        inv = pow(a, -1, b_mod)
        t0 = (rhs * inv) % b_mod

        current_a += current_mod * t0
        current_mod = new_mod

    if not has_solution:
        print("NaN")
    else:
        print(current_a if current_a <= N else "NaN")