#define _LIBCPP_DEBUG 0
#include<bits/stdc++.h>
using namespace std;
typedef long long int ll;
ll MOD = 1e9 + 7;



int main(void){

    ll N; cin>>N;
    vector<ll> A(2*N);
    for (int i = 0; i < 2 * N; ++i) {
        cin>>A[i];
    }

    vector<ll> SA(N), SA2(N);

    ll sum1=0;
    ll sum2 = 0;
    for (int i = 0; i < N; i++) {
        SA[i] += A[i*2] - A[i*2+1];
        SA2[i] += A[i*2+1] - A[i*2];
        sum1 += SA[i];
        sum2 += SA2[i];
    }

    for (int i = 0; i < N; ++i) {
        sum1 += SA[i];
    }

    ll ans = sum1;
    for (int i = 0; i < N; ++i) {
        sum1 = (sum1 - SA[i] - SA[i]) ;
        ans = max(ans, sum1);
    }

    for (int i = 0; i < N; ++i) {
        sum2 = (sum2 - SA2[i]-SA2[i]);
        ans = max(ans, sum2);
    }
    cout<<ans<<endl;
}