#include <bits/stdc++.h>
using namespace std;
int const N=2002;
int tab[N][N],spi[N],spj[N];
int main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
int n,m,zm;
cin>>n>>m;
for(int i=2;i<=n+1;i++) {
cin>>tab[i][0];
spi[i]=spi[i-1]+tab[i][0];
}
for(int i=2;i<=m+1;i++) {
cin>>tab[0][i];
spj[i]=spj[i-1]+tab[0][i];
}
for(int i=1;i<=n+1;i++){
for(int j=1;j<=m+1;j++){
if(j==1) tab[i][j]=spi[i-1]-tab[i-1][1]+tab[i][0];
else if(i==1) tab[i][j]=spj[j-1]-tab[1][j-1]+tab[0][j];
else tab[i][j]=max(spi[i]+spj[j-1]-tab[i][j-1]+tab[0][j],spi[i-1]+spj[j]-tab[i-1][j]+tab[i][0]);
}
}
/*for(int i=0;i<=n+1;i++){
for(int j=0;j<=m+1;j++){
cout<<tab[i][j]<<' ';
}cout<<endl;
}*/
cout<<tab[n+1][m+1]<<' ';
}
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