#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define FOR(i,a,b) for (auto i = (a); i <= (b); ++i)
#define NFOR(i,a,b) for(auto i = (a); i >= (b); --i)
#define all(x) (x).begin(), (x).end()
#define sz(x) int(x.size())
#define mp(i,a) make_pair(i,a)
#define pb(a) push_back(a)
#define bit(x,b) (x&(1LL<<b))
typedef long long int lli;
typedef pair <lli,lli> ii;
typedef pair <ii,lli> iii;
typedef vector <lli> vi;
int main()
{
lli n;
cin>>n;
ii av[n];
lli p[n+1],dp[n],m;
p[0]=0;
for(int i=0;i<n;++i)
cin>>av[i].F>>av[i].S;
sort(av,av+n);
for(int i=0;i<n;++i)
p[i+1]=p[i]+av[i].S;
dp[n-1]=av[n-1].S;
m=dp[n-1];
for(int i=n-2;i>=0;--i)
{
dp[i]=max(av[i].S,dp[i+1]+av[i].S-av[i+1].F+av[i].F);
m=max(m,dp[i]);
}
cout<<m<<endl;
return(0);
}
