#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define ll long long
void solve(){
int n;
cin >> n;
vector<array<ll,2>> k(n);
map<ll,ll> kk;
for(auto& [a,b]:k){
cin >> a >> b;
kk[a]+=b;
}
vector<array<ll,2>> k1;
for(auto [l1,r]:kk) k1.push_back({l1,r});
int l=0;
ll s=0;
ll max1=-1000000000000000000;
for(int i=0; i<k1.size(); i++){
s+=k1[i][1];
while(l<i && s-(k1[i][0]-k1[l+1][0])-k1[l][1]>=s-(k1[i][0]-k1[l][0])){
s-=k1[l][0];
l++;
}
max1=max(max1,s-(k1[i][0]-k1[l][0]));
}
cout << max1;
}
signed main(){
//freopen("input.txt","r",stdin);
//freopen("output.txt","w",stdout);
ios_base::sync_with_stdio(false);
cin.tie(nullptr);
cout.tie(nullptr);
int t=1;
//cin >> t;
while(t--){
solve();
}
}
