module math_mod
    ! This module include
    ! gcd, lcm
    ! extgcd
    use,intrinsic :: iso_fortran_env
    implicit none
    integer(int32),parameter:: byte = int64
contains
    function lcm(a, b) result(ret)
        integer(byte),intent(in):: a,b
        integer(byte):: ret

        ret = a*b/gcd(a,b)
    end function


    recursive function gcd(a, b) result(ret)
        integer(byte),intent(in):: a,b
        integer(byte):: ret

        if (mod(a,b) == 0_byte) then
            ret = b
            return
        end if
        ret = gcd(b,mod(a,b))
    end function


    recursive function extgcd(a, b, x, y) result(ret)
        ! solve:: ax + by = gcd(a,b) 
        ! input:: a, b
        ! output::  x, y, gcd(a,b)
        integer(byte),value:: a,b
        integer(byte),intent(out):: x,y
        integer(byte):: ret ! gcd(a,b)

        if (b==0_byte) then
            ret = a
            x = 1_byte
            y = 0_byte
        else
            ret = extgcd(b, mod(a,b), y, x)
            y = y - a/b * x
        end if
    end function

    recursive function mod_inv(a,m) result(ret)
        ! solve:: mod(ax, m) = 1
        !      => ax + my = 1
        ! input:: a,m
        ! output:: x <- モジュラ逆数
        integer(byte),intent(in):: a,m
        integer(byte):: ret, gcd_ma, x, y

        gcd_ma = extgcd(a,m,x,y)
        
        if (gcd_ma /= 1_byte) then
            ret = -1_byte
        else
            ret = modulo(x,m)
        end if
    end function


    function chineserem(input_b,input_m,md) result(ret)
        ! solve:: mod(b_1*k_1, m_1) = x
        !          :
        !         mod(b_n*k_n, m_n) = x を満たす最小のx
        ! input:: b(1:n), m(1:n)
        ! output:: x%md
        integer(byte):: input_b(:),input_m(:),md
        integer(byte), allocatable:: b(:), m(:)
        integer(byte):: ret, i, j, g, gi, gj
        integer(byte):: x, mmul

        allocate(b(0:size(input_b)), source=[0_byte, input_b])
        allocate(m(0:size(input_m)), source=[1_byte, input_m])
        do i=1_byte,size(b)-1_byte
            do j=i+1_byte,size(b)-1_byte
                g = gcd(m(i),m(j))
                ! print'(*(i0,1x))', i,j,b(i),b(j),b(i)-b(j),g
                if (mod(b(i)-b(j), g) /= 0_byte) then
                    ret = -1_byte
                    return
                end if
                m(i) = m(i) / g
                m(j) = m(j) / g
                gi = gcd(m(i),g)
                gj = g/gi
                m(i) = m(i)*gi
                m(j) = m(j)*gj
                b(i) = mod(b(i), m(i))
                b(j) = mod(b(j), m(j))
                ! print'(*(i0,1x))', i, j, m(i), m(j), b(i), b(j)
            end do
        end do
        ! print*, "b", b(:)
        ! print*, "m", m(:)
        mmul = 1_byte
        x = 0_byte
        do i=1_byte,size(b)-1_byte
            x = x + modulo((b(i)-x) * mod_inv(mmul,m(i)), m(i)) * mmul
            mmul = mmul*m(i)
            ! print*, i, x, mmul
        end do
        ! print*, x, mmul
        ret = modulo(x, md)
    end function
end module

program main
    use,intrinsic :: iso_fortran_env
    use math_mod
    implicit none
    integer(int64):: n, i, md=10_int64**9+7
    integer(int64),allocatable:: x(:), y(:)

    read*, n
    allocate(x(n), y(n))
    read*, (x(i), y(i), i=1,n)

    print'(i0)', chineserem(x,y,md)
end program main