// author : sentheta aka vanwij
#ifdef VANWIJ
#include"/home/user/code/bits/stdc++.h"
#define DBG 1
#else
#include"bits/stdc++.h"
#define DBG 0
#endif
using namespace std;
#define Int long long
#define V vector
#define pii pair<int,int>
#define ff first
#define ss second
static mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count());
#define pow2(x) (1LL<<(x))
#define msb(x) (63-__builtin_clzll(x))
#define bitcnt(x) (__builtin_popcountll(x))
#define nl '\n'
#define _ << ' ' <<
#define all(x) (x).begin(), (x).end()
#define rep(i,a,b) for(int i = (int)(a); i < (int)(b); i++)
#define cerr if(DBG) cout
#define dbg(x) {cerr << "?" << #x << " : " << (x) << endl << flush;}
#define int long long
// const Int MOD = 1e9+7;
const Int MOD = 998244353;
Int bpow(Int a,Int b){
Int ret = 1;
for(;b; a=a*a%MOD,b/=2) if(b&1) ret = ret*a%MOD;
return ret;
}
Int inv(Int a){return bpow(a,MOD-2);}
void solve(); int TC, ALLTC;
signed main(){
ios::sync_with_stdio(0); cin.tie(0); cout.tie(0); cout << fixed << setprecision(7);
// cin >> ALLTC; for(TC=1; TC<=ALLTC; TC++) solve(); return 0;
solve();
}
const int N = 5e5+5;
int n;
pii p[N];
int a[N], b[N];
int prf[N];
int best[N];
void solve(){
cin >> n;
rep(i,0,n){
cin >> p[i].ff >> p[i].ss;
}
sort(p, p+n);
rep(i,0,n){
a[i] = p[i].ff;
b[i] = p[i].ss;
}
rep(i,0,n){
prf[i] = b[i];
if(i){
prf[i] += prf[i-1];
}
}
for(int i=n-1; i>=0; i--){
best[i] = prf[i]-a[i];
if(i<n-1){
best[i] = max(best[i], best[i+1]);
}
}
int ans = 0;
rep(i,0,n){
int val = best[i] + a[i];
if(i) val -= prf[i-1];
ans = max(ans, val);
}
cout << ans << nl;
}
