#include <bits/stdc++.h>
#define int long long
using namespace std;
const int pp=5e5+5;
int a[pp],b[pp],n;
struct pl{
int val,s,maxx,minn;
};
pl dp[2][pp];
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
cin >> n;
for(int i=1;i<=n;i++) cin >> a[i] >> b[i];
dp[1][1].val=b[1];
dp[1][1].minn=a[1];
dp[1][1].maxx=a[1];
dp[1][1].s=b[1];
dp[0][1].val=-1e18;
dp[0][1].minn=1e18;
dp[0][1].maxx=-1e18;
dp[0][1].s=-1e18;
for(int i=2;i<=n;i++){
int prmax=0,prmin=0,prs=0,prval=0;
if(dp[0][i-1].val<dp[1][i-1].val){
prval=dp[1][i-1].val;
prmin=dp[1][i-1].minn;
prmax=dp[1][i-1].maxx;
prs=dp[1][i-1].s;
}
else{
prval=dp[0][i-1].val;
prmin=dp[0][i-1].minn;
prmax=dp[0][i-1].maxx;
prs=dp[0][i-1].s;
}
dp[0][i].val=prval;
dp[0][i].maxx=prmax;
dp[0][i].minn=prmin;
dp[0][i].s=prs;
int cmax=0,cmin=0;
if(a[i]>prmax) cmax=a[i];
else cmax=prmax;
if(a[i]<prmin) cmin=a[i];
else cmin=prmin;
dp[1][i].val=prs+b[i]-cmax+cmin;
dp[1][i].minn=cmin;
dp[1][i].maxx=cmax;
dp[1][i].s=prs+b[i];
}
cout << max(dp[0][n].val,dp[1][n].val);
return 0;
}
