#include //ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); //clock_t start=clock();clock_t end=clock();cout<<(double)(end-start)/CLOCKS_PER_SEC< pii; typedef pair ppii; typedef pair pipi; typedef pair pll; typedef pair ppll; typedef pair plpl; typedef tuple tl; ll mod=1000000007; ll mod2=998244353; ll mod3=1000003; ll mod4=998244853; ll inf=1LL<<60; double pi=3.141592653589793238462643383279L; double eps=1e-10; #define rep(i,m,n) for(int i=m;i=m;i--) #define srep(itr,st) for(auto itr=st.begin();itr!=st.end();itr++) #define Max(a,b) a=max(a,b) #define Min(a,b) a=min(a,b) int dh[4]={1,-1,0,0}; int dw[4]={0,0,1,-1}; int ddh[8]={-1,-1,-1,0,0,1,1,1}; int ddw[8]={-1,0,1,-1,1,-1,0,1}; ll gcd(ll a,ll b){ if(a0){ if(k&1)ret*=now; now*=now; k/=2; } return ret; } ll beki(ll n,ll k,ll md){ ll ret=1; ll now=n; while(k>0){ if(k%2==1){ ret*=now; ret%=md; } now*=now; now%=md; k/=2; } return ret; } ll gyaku(ll n,ll md){ return beki(n,md-2,md); } int main(){ ios::sync_with_stdio(false);cin.tie(0);cout.tie(0); ll n;cin>>n; ll sum[2*n+1]; sum[0]=0; rep(i,0,2*n){ ll a;cin>>a; if(i%2==0)sum[i+1]=sum[i]+a; else sum[i+1]=sum[i]-a; } ll ans=-inf; for(int i=0;i<=2*n;i+=2){ ll s=sum[i]-(sum[2*n]-sum[i]); Max(ans,s); } cout<