#include<bits/stdc++.h>
using namespace std;
#define INIT ios_base :: sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());
#define mp make_pair
#define pb push_back
#define ft first
#define sc second
#define ll long long
#define pii pair<int, int>
#define count_bits __builtin_popcount
#define int ll
int t, n, m, k;
pii ab[500010];
int32_t main(){
INIT
cin>>n;
for(int i=1; i<=n; i++){
cin>>ab[i].ft>>ab[i].sc;
}
sort(ab+1, ab+n+1);
int inf=1e17;
int mn=inf;
int res=0;
int sum=0;
for(int i=n; i>=1; i--){
sum+=ab[i].sc;
mn=min(mn, sum+ab[i].ft-ab[i].sc);
res=max( sum-mn+ab[i].ft, res);
}
cout<<res;
return 0;
}
