def crt(r,m):
    def extgcd(a,b):
        if b==0:
            return 1,0,a
        c,x,g=extgcd(b,a%b)
        return x,c-a//b*x,g
    
    r0,m0=0,1
    
    for i in range(len(r)):
        p,q,g=extgcd(m0,m[i])

        if r0%g!=r[i]%g:
            return 0,0

        s=(r[i]-r0)//g

        l=m0//g*m[i]
        x=(s*m0*p+r0)%l

        m0=l
        r0=x
    
    return r0,m0

MOD=10**9+7
N=int(input())
X,Y=[],[]
for _ in range(N):
    x,y=map(int,input().split())
    X.append(x)
    Y.append(y)

r,m=crt(X,Y)

if r==0 and m==0:
    print(-1)
elif r==0:
    print(m%MOD)
else:
    print(r%MOD)