class UnionFind
  def initialize(n)
    @size = Array.new(n, 1)
    @rank = Array.new(n, 0)
    @parent = []

    (0..n).each do |i|
      @parent[i] = i
    end
  end

  def find(x)
    if @parent[x] == x
      x
    else
      @parent[x] = find(@parent[x])
    end
  end

  def unite(x, y)
    x = find(x)
    y = find(y)
    return if x == y

    if @rank[x] < @rank[y]
      @parent[x] = y
      @size[y] += @size[x]
    else
      @parent[y] = x
      @size[x] += @size[y]

      @rank[x] += 1 if @rank[x] == @rank[y]
    end
  end

  def same?(x, y)
    find(x) == find(y)
  end

  def size(x)
    @size[find(x)]
  end
end

N = gets.to_i

goods = N.times.map { gets.split.map(&:to_i) }
E = []
S = N

N.times do |i|
  c, d = goods[i]
  E << [i, N, c]

  if i + 1 < N
    nc, nd = goods[i + 1]
    E << [i, i + 1, nd]
  end
end

E.sort_by! { |_, _, cost| cost }
uf = UnionFind.new(N + 2)
ans = goods.map(&:first).sum

E.each do |u, v, cost|
  next if uf.same?(u, v)

  uf.unite(u, v)
  ans += cost
end

puts ans