#include <fstream>
#include <algorithm>
#define NMAX 100005
using namespace std;
ifstream in("heavymetal.in");
ofstream out("heavymetal.out");

pair<int, int> v[NMAX];
int dp[NMAX], i, n, x, y, st, dr, mij;

bool cmp(pair<int, int> a, pair<int, int> b){
    if(a.second < b.second)
        return 1;
    else if (a.second == b.second && a.first < b.first)
        return 1;
    return 0;
}

void read(){
    int i;
    in >> n;
    for(i = 1; i <= n; i++)
        in >> v[i].first >> v[i].second;
}

void solve(){

    sort(v + 1, v + n + 1, cmp);
    for(i = 1; i <= n; i++) {
        x = v[i].first, y = v[i].second;
        st = 1, dr = i - 1;
        while(st <= dr) {
            mij = (st + dr) / 2;
            if(v[mij].second <= x)
                st = mij + 1;
            else
                dr = mij - 1;
        }
        dp[i] = max(dp[i - 1], dp[dr] + abs(x - y));
    }
    out << dp[n];
}

int main(){

    read();
    solve();
    return 0;
}