#include<bits/stdc++.h> using namespace std; typedef long long ll; ll readint(){ ll x=0,f=1; char ch=getchar(); while(ch<'0'||ch>'9'){if(ch=='-')f=-1;ch=getchar();} while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();} return x*f; } struct node{ ll x,y; bool operator<(const node c)const{ if(x==c.x) return y<c.y; return x<c.x; } }k[500005]; ll n; ll s[500005]; int main(){ n=readint(); for(int i=1;i<=n;i++) k[i].x=readint(),k[i].y=readint(); sort(k+1,k+n+1); for(int i=1;i<=n;i++) s[i]=s[i-1]+k[i].y; ll ans=0,now=0; for(int i=1;i<=n;i++){ now=max(now,k[i].x-s[i-1]); ans=max(ans,s[i]-k[i].x+now); } cout<<ans<<endl; return 0; }