a,b = map(int,input().split())
mod = 10**9+7
if a*b == 0:
    if a%2 or b%2:
        print((a+b)%mod)
    else:
        print((a+b+1)%mod)
    exit()
if a > b:
    a,b = b,a
if a%2 == b%2:
    l = (a-b)//2
    r = (b-a)//2
    ans = (r-l+1)*(2*a+1)%mod

    ans += (2*a)*((2*a+1)//2)%mod

else:
    if a%2:
        l = (a-b+1)//2
        r = (b-a-1)//2
        ans = (r-l+1)*(2*a+1)%mod
        ans += (2*a)*((2*a+1)//2)%mod
        print(-1)
    else:
        l = (a-b+1)//2
        r = (b-a-1)//2
        ans = (r-l+1)*(2*a+1)%mod
        ans += (2*a+2)*(a)%mod
        print(-1)

print(ans%mod)