import sequtils,strutils,algorithm
type
    unionfindtree[I : static[int]] = array[I,int]

proc initUT(I : static[int]):unionfindtree[I] =
    var res : unionfindtree[I]
    for i in 0..<I:
        res[i] = i
    return res
    
proc find(U : var unionfindtree; a : int, b :int): bool=
    var
        s = a
        t = b
    while s != U[s]:
        s = U[s]
    while t != U[t]:
        t = U[t]
    var
        s2 = a
        t2 = b
        p : int
    while s2 != s:
        p = U[s2]
        U[s2] = s
        s2 = p
    while t2 != t:
        p = U[t2]
        U[t2] = t
        t2 = p
    return s == t
    
proc union(U : var  unionfindtree; a : int ; b : int)=
    if U.find(a,b):
        return
    var
        s = a
        t = b
        t2 : int
    while s != U[s]:
        s = U[s]
    while t != U[t]:
        t2 = U[t]
        U[t] = s
        t = t2
    U[t] = s
proc root(U : unionfindtree, a :int):int=
    var
        s = a
    while s != U[s]:
        s = U[s]
    return s

var
    N = stdin.readline.parseInt
    BIT = initUT(100010)
    c,d,ans : int64

type
    edge = tuple[a : int ,b : int,c : int64]

var
    edges = newSeq[edge](0)

for i in 1..N:
    (c, d) =stdin.readline.split.map(parseBiggestInt)
    if i != 1:
        edges.add((i, i - 1, d))
    edges.add((i, 0, c))
    ans += c

edges = edges.sortedByIt(it.c)
for e in edges:
    if BIT.find(e.a,e.b) == false:
        ans += e.c
        BIT.union(e.a,e.b)

echo ans