package main

import (
    "fmt"
    "math"
    "sort"
)

const N int = 50010
var s [N]int
var w [N]int

type Pair struct {
    s int
    w int
}

type PairArray []*Pair

func (p PairArray) Len() int {
    return len(p)
}

func (p PairArray) Less(i, j int) bool {
    return p[i].s + (p)[i].w < (p)[j].s + (p)[j].w
}

func (p PairArray) Swap(i, j int) {
    (p)[i], (p)[j] = (p)[j], (p)[i]
}

func main() {
    var n int
    fmt.Scanf("%d", &n)

    mapval := make([]*Pair, 0, n)
    for i := 0; i < n; i++ {
        fmt.Scanf("%d", &s[i])
        fmt.Scanf("%d", &w[i])

        mapval = append(mapval, &Pair{s:s[i], w:w[i]})
    }

    sort.Sort(PairArray(mapval))
    res := math.MinInt32
    sum := 0
    for i := 0; i < n; i++ {
        if res < sum - mapval[i].w {
            res = sum - mapval[i].w
        }
        sum += mapval[i].s
    }

    fmt.Printf("%d\n", res)
}