#include <bits/stdc++.h>
#define DIM 500010
#define INF 2000000000000000000LL
using namespace std;
struct idk{
long long a,b;
} v[DIM];
long long aint[DIM*4],sp[DIM],sol;
int n,i;
inline int cmp (idk a, idk b){
return a.a < b.a;
}
void build (int nod, int st, int dr){
if (st == dr){
aint[nod] = sp[st] - v[st].a;
return;
}
int mid = (st+dr)>>1;
build (nod<<1,st,mid);
build ((nod<<1)|1,mid+1,dr);
aint[nod] = max (aint[nod<<1],aint[(nod<<1)|1]);
}
long long query (int nod, int st, int dr, int x, int y){
if (x <= st && dr <= y)
return aint[nod];
int mid = (st+dr)>>1;
long long sol_st = -INF, sol_dr = -INF;
if (x <= mid)
sol_st = query (nod<<1,st,mid,x,y);
if (y > mid)
sol_dr = query ((nod<<1)|1,mid+1,dr,x,y);
return max (sol_st,sol_dr);
}
int main (){
//ifstream cin ("date.in");
//ofstream cout ("date.out");
cin>>n;
sol = -INF;
for (i=1;i<=n;i++){
cin>>v[i].a>>v[i].b;
sol = max (sol,v[i].b);
}
sort (v+1,v+n+1,cmp);
for (i=1;i<=n;i++)
sp[i] = sp[i-1] + v[i].b;
build (1,1,n);
for (i=1;i<n;i++)
sol = max (sol,v[i].a - sp[i-1] + query(1,1,n,i+1,n));
cout<<sol;
return 0;
}
