#include<bits/stdc++.h>
#define M 1004
using namespace std;
 
int n, a[M], b[M], dp1[M], dp2[M];
 
int main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);     cout.tie(0);
 
    cin >> n;
    for(int i = 1; i <= n; i++)
        cin >> a[i] >> b[i];
    dp1[1] = b[1];
    dp2[1] = a[1];
    for(int i = 2; i <= n; i++)
    {
        dp1[i] = max(dp1[i - 1] + b[i] + abs(a[i] - a[i - 1]), dp2[i - 1] + b[i] + abs(a[i] - b[i - 1]));
        dp2[i] = max(dp2[i - 1] + a[i] + abs(b[i] - b[i - 1]), dp1[i - 1] + a[i] + abs(b[i] - a[i - 1]));
    }
    cout << max(dp1[n], dp2[n]);
}
 

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NSAKMiA1IAozIDggCjEgMTAgCjcgMTQgCjIgNQo=

5 
2 5 
3 8 
1 10 
7 14 
2 5