#include <bits/stdc++.h>
#pragma GCC optimize ("Ofast", "unroll-loops")
using namespace std;
#define ll long long
#define int ll
#define FOR(i,a,b) for (int i = (a); i<(b); i++)
#define REP(i,n) FOR(i,0,n)
#define REP1(i,n) FOR(i,1,n+1)
#define RREP(i,n) for (int i=(n)-1; i>=0; i--)
#define f first
#define s second
#define pb push_back
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)(x.size())
#define SQ(x) (x)*(x)
#define pii pair<int, int>
#define pdd pair<double ,double>
#define pcc pair<char, char>
#define endl '\n'
//#define TOAD
#ifdef TOAD
#define bug(x) cerr<<__LINE__<<": "<<#x<<" is "<<x<<endl
#define IOS()
#else
#define bug(...)
#define IOS() ios::sync_with_stdio(0), cin.tie(0), cout.tie(0)
#endif
const ll inf = 1ll<<60;
const int iinf=2147483647;
const ll mod = 1e9+7;
const ll maxn=1e5+5;
const double PI=acos(-1);
ll pw(ll x, ll p, ll m=mod){
ll ret=1;
while (p>0){
if (p&1){
ret*=x;
ret%=m;
}
x*=x;
x%=m;
p>>=1;
}
return ret;
}
ll inv(ll a, ll m=mod){
return pw(a,m-2);
}
//=======================================================================================
bool cmp(pii x, pii y){
if (x.f==y.f) return x.s<y.s;
return x.f<y.f;
}
signed main (){
IOS();
int n; cin>>n;
vector<pii> vc(n+1);
vector<int> pf(n+1), sf(n+1);
REP1(i,n) cin>>vc[i].f>>vc[i].s;
sort(ALL(vc), cmp);
REP1(i,n){
pf[i]=pf[i-1]+vc[i].s;
}
for (int i=n; i>=1; i--){
if (i==n){
sf[i]=pf[i]-vc[i].f;
continue;
}
sf[i]=max(sf[i+1], pf[i]-vc[i].f);
}
int ans=0;
REP1(i,n){
ans=max(ans, sf[i]-pf[i-1]+vc[i].f);
}
cout<<ans<<endl;
}
