import math

def main():
    import sys
    input = sys.stdin.read().split()
    ptr = 0
    N = int(input[ptr])
    ptr += 1
    M = int(input[ptr])
    ptr += 1
    list_bc = []
    for _ in range(M):
        B = int(input[ptr])
        C = int(input[ptr + 1])
        ptr += 2
        list_bc.append((B, C))
    
    x = 0
    mod = 1
    for B, C in list_bc:
        d = (C - x) % B
        g = math.gcd(mod, B)
        if d % g != 0:
            print("NaN")
            return
        
        a_prime = mod // g
        m_prime = B // g
        d_prime = d // g
        
        try:
            inv = pow(a_prime, -1, m_prime)
        except ValueError:
            print("NaN")
            return
        
        k0 = (d_prime * inv) % m_prime
        x += k0 * mod
        mod = (mod * B) // g
    
    x = x % mod
    if x <= N:
        print(x)
    else:
        print("NaN")

if __name__ == "__main__":
    main()