n, k = io.read('n'), io.read('n')
x, y = {}, {}
for i = 1, n do x[i], y[i] = io.read('n'), io.read('n') end

-- Discretize
rx, ry = {}, {}
for i = 1, n do rx[i], ry[i] = {x[i], i}, {y[i], i} end
pair_cmp = function (lhs, rhs) return lhs[1] < rhs[1] end
table.sort(rx, pair_cmp)
table.sort(ry, pair_cmp)
for i = 1, n do x[rx[i][2]], y[ry[i][2]] = i, i end
for i = 1, n do rx[i], ry[i] = rx[i][1], ry[i][1] end

-- O(n^4)
-- Prefix sum
p = {}
for i = 0, n do
    p[i] = {}
    for j = 0, n do p[i][j] = 0 end
end
for i = 1, n do p[x[i]][y[i]] = 1 end
for i = 1, n do
    for j = 1, n do
        p[i][j] = p[i][j] + p[i - 1][j] + p[i][j - 1] - p[i - 1][j - 1]
    end
end

-- Iteration
ans = 1 << 62
for l = 1, n do
    for r = l + 1, n do
        for d = 1, n do
            for u = d + 1, n do
                if p[r][u] - p[l - 1][u] - p[r][d - 1] + p[l - 1][d - 1] >= k then
                    ans = math.min(ans, (rx[r] - rx[l]) * (ry[u] - ry[d]))
                end
            end
        end
    end
end

print(ans)
