#include <bits/stdc++.h>
#define fast cin.tie(0);cout.tie(0);ios_base::sync_with_stdio(false)
#define pb push_back
#define ppb pop_back
#define fi first
#define se second
#define sp " "
#define endl "\n"
#define mod 1000000007
#define MAXN 500005
#define MAXM 1000006
#define inf 1e18
#define INF 0x3f
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
#define debug(x) for(auto& a: x) cout << a << " "
using namespace std;
typedef long long int lo;
lo n,m,q,k,l,a,b;
lo arr[MAXN],deg[MAXN],pre[MAXN];
vector<lo> v[MAXN];
pair<lo,lo> item[MAXN];
lo kayit[MAXN];
string s[1005];
set<lo> st[MAXN];
lo cnt;
lo p;
void solve(){
cin >> n;
for (int i = 1; i <= n; ++i)
{
cin >> item[i].fi >> item[i].se;
}
sort(item+1,item+n+1);
for (int i = 1; i <= n; ++i)
{
pre[i] = pre[i-1] + item[i].se;
}
lo mn=inf, ans=0;
for(int i = 1; i <= n; i++){
mn = min(mn, pre[i-1] - item[i].fi);
// cout << (pre[i] - item[i].fi) << sp << mn << endl;
ans = max(ans, (pre[i] - item[i].fi) - mn);
}
cout << ans << endl;
}
int main()
{
// cout << fixed << setprecision(12);
// freopen("feast.in","r",stdin);
// freopen("feast.out","w",stdout);
// fast;
int t = 1;
// cin >> t;
while(t--)
{
solve();
}
}
