import sys
from math import gcd

def crt(a1, m1, a2, m2):
    g = gcd(m1, m2)
    if (a2 - a1) % g != 0:
        return None
    m_div = m1 // g
    n_div = m2 // g
    inv = pow(m_div, -1, n_div)
    k = (( (a2 - a1) // g ) * inv) % n_div
    lcm = m_div * m2  # lcm(m1, m2)
    x0 = (a1 + k * m1) % lcm
    return (x0, lcm)

def main():
    input = sys.stdin.read().split()
    ptr = 0
    N = int(input[ptr])
    ptr += 1
    M = int(input[ptr])
    ptr += 1
    B = []
    C = []
    for _ in range(M):
        b = int(input[ptr])
        c = int(input[ptr + 1])
        ptr += 2
        B.append(b)
        # Normalize C
        c_mod = c % b
        C.append(c_mod)
    # Initial conditions: x ≡ 0 mod 1
    current_a = 0
    current_mod = 1
    for i in range(M):
        b = B[i]
        c = C[i]
        res = crt(current_a, current_mod, c, b)
        if res is None:
            print("NaN")
            return
        current_a, current_mod = res
    # Check if current_a is within N
    if current_a <= N:
        print(current_a)
    else:
        print("NaN")

if __name__ == "__main__":
    main()