#include<bits/stdc++.h>
using namespace std;
#define ll long long
#define ff first
#define ss second
#define pb push_back
int main() {
ios_base::sync_with_stdio(false); cin.tie(0); cout.tie(0);
float db,y[100000],x[1000000];
long long t,i,l,n,mod=1000000007,c,a,m,e,d,b,k,j,w[300005],f,z[300005],g=0,q,p,r[300005],h,o[1001][1001];
map<ll,ll>blp;
set<ll>st;
string s,sa[200005],ta[200005],sn,sm,sk,cr,sx,sy;
pair<ll,ll>pr[300005];
char ch[200005];
vector<ll>ret,v;
cin>>n;
for (i=1; i<=n; i++){
cin>>z[i]>>r[i];
pr[i].ff=z[i];
pr[i].ss=r[i];
}
e=0;
sort (pr+1, pr+1+n);
w[0]=0;
for (i=1; i<=n; i++){
w[i]=w[i-1]+pr[i].ss;
}
for (i=1; i<=n; i++){
for (j=i; j<=n; j++){
o[i][j]=w[j]-w[i]+pr[i].ss-pr[j].ff+pr[i].ff;
e=max(e,o[i][j]);
}
}
cout<<e;
}
