import sys
import math

def extended_gcd(a, b):
    if b == 0:
        return (a, 1, 0)
    else:
        g, x, y = extended_gcd(b, a % b)
        return (g, y, x - (a // b) * y)

def main():
    N = int(sys.stdin.readline())
    M = int(sys.stdin.readline())
    congruences = []
    for _ in range(M):
        B, C = map(int, sys.stdin.readline().split())
        c = C % B
        congruences.append((B, c))
    
    a = 0
    m = 1
    for (B, c) in congruences:
        d = math.gcd(m, B)
        if (c - a) % d != 0:
            print("NaN")
            return
        m1 = m // d
        B1 = B // d
        c_div = (c - a) // d
        
        g, x, y = extended_gcd(m1, B1)
        k0 = (c_div * x) % B1
        new_a = a + k0 * m
        new_m = m * B // d
        new_a %= new_m
        a, m = new_a, new_m
    
    if a > N:
        print("NaN")
    else:
        print(a)
    print()

if __name__ == '__main__':
    main()