import sys, re

from collections import deque, defaultdict, Counter

from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2

from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby

from operator import itemgetter, mul

from copy import deepcopy

from string import ascii_lowercase, ascii_uppercase, digits

from bisect import bisect, bisect_left, insort, insort_left

from fractions import gcd

from heapq import heappush, heappop

from functools import reduce

def input(): return sys.stdin.readline().strip()

def INT(): return int(eval(input()))

def MAP(): return list(map(int, input().split()))

def LIST(): return list(map(int, input().split()))

def ZIP(n): return list(zip(*(MAP() for _ in range(n))))

sys.setrecursionlimit(10 ** 9)

INF = float('inf')

mod = 10**9 + 7

#from decimal import *



N = INT()

AB = [LIST() for _ in range(N)]



AB.extend([[0, INF], [INF, 0]])



AB.sort(key = lambda x:x[0])



ans = 0

for i in range(1, N+2):

	ans += min(AB[i][0]-AB[i-1][0], AB[i-1][1]-AB[i][1])



print(ans)
import sys, re

from collections import deque, defaultdict, Counter

from math import ceil, sqrt, hypot, factorial, pi, sin, cos, tan, asin, acos, atan, radians, degrees#, log2

from itertools import accumulate, permutations, combinations, combinations_with_replacement, product, groupby

from operator import itemgetter, mul

from copy import deepcopy

from string import ascii_lowercase, ascii_uppercase, digits

from bisect import bisect, bisect_left, insort, insort_left

from fractions import gcd

from heapq import heappush, heappop

from functools import reduce

def input(): return sys.stdin.readline().strip()

def INT(): return int(eval(input()))

def MAP(): return list(map(int, input().split()))

def LIST(): return list(map(int, input().split()))

def ZIP(n): return list(zip(*(MAP() for _ in range(n))))

sys.setrecursionlimit(10 ** 9)

INF = float('inf')

mod = 10**9 + 7

#from decimal import *



N = INT()

AB = [LIST() for _ in range(N)]

AB.sort(key = lambda x: x[0])

print((AB[-1][0] + AB[-1][1]))
import sys, re
from collections import deque, defaultdict, Counter
from math import (
    ceil,
    sqrt,
    hypot,
    factorial,
    pi,
    sin,
    cos,
    tan,
    asin,
    acos,
    atan,
    radians,
    degrees,
)  # , log2
from itertools import (
    accumulate,
    permutations,
    combinations,
    combinations_with_replacement,
    product,
    groupby,
)
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce


def input():
    return sys.stdin.readline().strip()


def INT():
    return int(eval(input()))


def MAP():
    return list(map(int, input().split()))


def LIST():
    return list(map(int, input().split()))


def ZIP(n):
    return list(zip(*(MAP() for _ in range(n))))


sys.setrecursionlimit(10**9)
INF = float("inf")
mod = 10**9 + 7
# from decimal import *
N = INT()
AB = [LIST() for _ in range(N)]
AB.extend([[0, INF], [INF, 0]])
AB.sort(key=lambda x: x[0])
ans = 0
for i in range(1, N + 2):
    ans += min(AB[i][0] - AB[i - 1][0], AB[i - 1][1] - AB[i][1])
print(ans)

import sys, re
from collections import deque, defaultdict, Counter
from math import (
    ceil,
    sqrt,
    hypot,
    factorial,
    pi,
    sin,
    cos,
    tan,
    asin,
    acos,
    atan,
    radians,
    degrees,
)  # , log2
from itertools import (
    accumulate,
    permutations,
    combinations,
    combinations_with_replacement,
    product,
    groupby,
)
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left, insort, insort_left
from fractions import gcd
from heapq import heappush, heappop
from functools import reduce


def input():
    return sys.stdin.readline().strip()


def INT():
    return int(eval(input()))


def MAP():
    return list(map(int, input().split()))


def LIST():
    return list(map(int, input().split()))


def ZIP(n):
    return list(zip(*(MAP() for _ in range(n))))


sys.setrecursionlimit(10**9)
INF = float("inf")
mod = 10**9 + 7
# from decimal import *
N = INT()
AB = [LIST() for _ in range(N)]
AB.sort(key=lambda x: x[0])
print((AB[-1][0] + AB[-1][1]))

-AB.extend([[0, INF], [INF, 0]]) -ans = 0 -for i in range(1, N + 2): -    ans += min(AB[i][0] - AB[i - 1][0], AB[i - 1][1] - AB[i][1]) -print(ans) +print((AB[-1][0] + AB[-1][1]))