#include <bits/stdc++.h>
#define IOS ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#define int long long
using namespace std;
int n, dp[500001];
pair <int, int> pr[500001];
int solve(int i, int s, int st, int en)
{
if (i == n)
{
if (s == -1)
return -1e18;
return s-(en-st);
}
int ch1 = solve(i+1, s, st, en), ch2;
if (st == -1)
ch2 = solve(i+1, s+pr[i].second, pr[i].first, pr[i].first);
else
ch2 = solve(i+1, s+pr[i].second, st, pr[i].first);
return max(ch1, ch2);
}
signed main()
{
IOS;
cin >> n;
for (int i = 0; i < n; i++)
cin >> pr[i].first >> pr[i].second;
sort(pr, pr+n);
cout << solve(0, 0, -1, -1);
return 0;
}
