local read = setmetatable({}, {__index = function(t, k) local a = {} for i=1,#k do table.insert(a, '*'..string.sub(k, i, i)) end local r = io.read local u = table.unpack or unpack return function() return r(u(a)) end end})
read.N = function(N) local t={} for i=1,N do t[i]=read.n() end return t end
string.totable = function(s) local t={} local u=string.sub for i=1,#s do t[i] = u(s, i, i) end return t end
string.split = function(s) local t={} for w in string.gmatch(s, "[^%s]+") do table.insert(t, w) end return (table.unpack or unpack)(t) end
local function array(dimension, default_val) local n=dimension local m={}if default_val~=nil then m[1]={__index=function()return default_val end}end for i=2,n do m[i]={__index=function(p, k)local c=setmetatable({},m[i-1])rawset(p,k,c)return c end}end return setmetatable({},m[n])end
----

-- returns (b^n) % m
local function modpow(b, n, m)
    if n == 0 then
        return 1
    elseif n % 2 == 0 then
        -- be careful about overflow of b*b
        return modpow(b * b % m, n//2, m)
    else
        return b * modpow(b, n - 1, m) % m
    end
end

-- returns n! % m
local function modfactorial(n, m)
    local a = 1
    for i=1, n do
        a = a * i % m
    end
    return a
end

local function make_mod_nCr(nmax, m)
    -- Create n! table
    local mfac = {}
    mfac[0] = 1
    for i=1,nmax do
        mfac[i] = mfac[i-1] * i % m
    end
    -- Create (n!)^(-1) table
    -- (n!)^(-1) ≡ (n!)^(m - 2)  <mod m>
    local invmfac = {}
    invmfac[nmax] = modpow(mfac[nmax], m - 2, m)
    for i=nmax,1,-1 do
        -- ((a-1)!)^(-1) ≡ a * (a!)^(-1)  <mod m>
        invmfac[i-1] = i * invmfac[i] % m
    end
    -- returns nCr % m
    local function mod_nCr(n, r)
        -- nCr ≡ n! * (r!)^(-1) * ((n-r)!)^(-1)  <mod m>
        local a = mfac[n] * invmfac[r] % m
        a = a * invmfac[n-r] % m
        return a
    end
    return mod_nCr
end

---------------------------------------
local floor = math.floor
local MOD = floor(10^9)+7
local pow2 = {}
local function make_pow2(n)
    pow2[0] = 1
    for i=1,32 do
        pow2[i] = floor(2^i) % MOD
    end
    local function modpow2(n)
        if pow2[n] then
            return pow2[n]
        end
        if n % 2 == 0 then
            pow2[n] = modpow2(n//2) * modpow2(n//2) % MOD
        else
            pow2[n] = (modpow2(n//2) * modpow2(n//2) % MOD) * 2 % MOD
        end
        return pow2[n]
    end
    return modpow2(n)
end
--
local function nCr_modM(n, r)
    if r > n then
        return 0
    end
    if r > n/2 then
        r = n - r
    end
    local a = 1
    for i=n, n-r+1, -1 do
        a = (a * i) % MOD
    end
    local denom -- modfactorial(r, MOD)
    do
        local nmax = r
        local m = MOD
        -- Create n! table
        local mfac = {}
        mfac[0] = 1
        for i=1,nmax do
            mfac[i] = mfac[i-1] * i % m
        end
        -- Create (n!)^(-1) table
        -- (n!)^(-1) ≡ (n!)^(m - 2)  <mod m>
        local invmfac = {}
        invmfac[nmax] = modpow(mfac[nmax], m - 2, m)
        for i=nmax,1,-1 do
            -- ((a-1)!)^(-1) ≡ a * (a!)^(-1)  <mod m>
            invmfac[i-1] = i * invmfac[i] % m
        end
        denom = invmfac[r]
    end
    return a * denom % MOD
end
----
local n, a, b = read.nnn()
make_pow2(n)
local S = pow2[n] - 1
local NGa = nCr_modM(n, a)
local NGb = nCr_modM(n, b)
--print("n!", S)
--print("nCa", NGa)
--print("nCb", NGb)
local ans = S - NGa - NGb
while ans < 0 do
    ans = ans + MOD
end
print(ans)

Measured memory_bytes: 24936