#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define srep(i,s,t) for (int i = s; i < t; ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
#define yn {puts("YES");}else{puts("NO");}
#define MAX_N 200005

int main() {
    ll n;
    cin >> n;
    ll a[n*2];
    rep(i,n*2)cin >> a[i];
    ll b[n] = {};
    ll sum = 0;
    rep(i,n){
        b[i] = a[i*2] - a[i*2+1];
        sum += b[i];
    }

    ll ans = sum;
    // rep(i,n)cout << b[i];

    drep(i,n){
        sum -= 2 * b[i];
        ans = max(ans, sum);
    }

    cout << ans << endl;
    return 0;
}