#include <bits/stdc++.h>
using namespace std;
int const MAX=5e5+5;
struct art{
long long val;
long long sz;
bool operator<(art ot){
return sz<ot.sz;
}
}v[MAX];
int n;
void read(){
cin>>n;
int i;
for(i=1;i<=n;++i)
cin>>v[i].sz>>v[i].val;
sort(v+1,v+n+1);
}
void maxself(long long& x,long long val){
if(x<val)
x=val;
}
long long solve(){
int i;
long long rasp=v[1].val;
long long act=v[1].val;
for(i=2;i<=n;++i){
act=max(act+v[i].val-v[i].sz+v[i-1].sz,v[i].val);
maxself(rasp,act);
}
return rasp;
}
void write(long long ans){
cout<<ans;
}
int main()
{
read();
write(solve());
return 0;
}
