#pragma GCC optimize("O3")
#pragma GCC target("sse4")
#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef long double ld;
typedef pair<int, int> pi;
typedef pair<ll, ll> pl;
typedef pair<ld, ld> pd;
typedef vector<int> vi;
typedef vector<bool> vb;
typedef vector<vector<int>> vvi;
typedef vector<ld> vd;
typedef vector<ll> vl;
typedef vector<pi> vpi;
typedef vector<pl> vpl;
#define FOR(i, a, b) for (ll i = a; i < (b); i++)
#define F0R(i, a) for (ll i = 0; i < (a); i++)
#define FORd(i, a, b) for (ll i = (b)-1; i >= a; i--)
#define F0Rd(i, a) for (ll i = (a)-1; i >= 0; i--)
#define trav(a, x) for (auto &a : x)
#define uid(a, b) uniform_int_distribution<int>(a, b)(rng)
#define len(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define fst first
#define nl endl
#define sec second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define ins insert
const int MOD = 1000000007;
const int MX = INT_MAX;
const int MN = INT_MIN;
void init()
{
#ifndef ONLINE_JUDGE
freopen("input.in", "r", stdin);
freopen("output.out", "w", stdout);
#endif
}
void fastIO()
{
ios_base::sync_with_stdio(0);
cin.tie(0);
}
void solve()
{
ll n;cin>>n;
vpl arr(n);
FOR(i,0,n)cin >> arr[i].first >> arr[i].second;//size,value
sort(all(arr));
ll ans = 0;
vpl dp(n,{0,0});//sum,min size
dp[0] = {arr[0].second,arr[0].first};
FOR(i,1,n){
dp[i] = {arr[i].second,arr[i].first};
ans = max(ans,dp[i].first);
ll sum = dp[i-1].first + arr[i].second;
ll possible = sum - arr[i].first + dp[i-1].second;
if(dp[i].first < possible){
dp[i] = {sum,dp[i-1].second};
}
ans = max(ans,possible);
}
// FOR(i,0,n){
// cout << i << " " << dp[i].first << " " << dp[i].second << endl;
// }
cout << ans << endl;
}
int main()
{
fastIO();
// init();
int t = 1;
// cin >> t;
while (t--)
solve();
return 0;
}
