#include <bits/stdc++.h>
using namespace std;
#define int long long
#define all(x) x.begin(), x.end()
#define inf (int)3e18
#define ff first
#define ss second
using vi = vector<int>;
using vii = vector<pair<int, int>>;
using vvi = vector<vector<int>>;
using pii = pair<int, int>;
mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
const int MAX = 5e5 + 5;
array<int, 3> dp[MAX];
int a[MAX], b[MAX];
void solve()
{
int n;
cin >> n;
for (int i = 1; i <= n; i++)
cin >> a[i] >> b[i];
dp[1][0] = b[1];
dp[1][1] = a[1];
dp[1][2] = a[1];
for (int i = 2; i <= n; i++)
{
// If we dont take -> s
// If we take -> sn
int S = dp[i - 1][0] - dp[i - 1][1] + dp[i - 1][2];
int Sn = dp[i - 1][0] + b[i] - max(dp[i - 1][1], a[i]) + min(dp[i - 1][2], a[i]);
if (Sn > S)
{
dp[i][0] = dp[i - 1][0] + b[i];
dp[i][1] = max(dp[i - 1][1], a[i]);
dp[i][2] = min(dp[i - 1][2], a[i]);
}
else
{
dp[i] = dp[i - 1];
}
}
// for (int i = 1; i <= n; i++)
// {
// cout << dp[i][0] << ' ' << dp[i][1] << ' ' << dp[i][2] << '\n';
// }
cout << dp[n][0] - dp[n][1] + dp[n][2];
}
signed main()
{
ios::sync_with_stdio(0);
cin.tie(0);
int tt = 1;
// cin >> tt;
while (tt--)
solve();
}
