#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <iostream>
using namespace std;
int tempo_massimo(int N, int a[], int b[]){
    int v0=0;
    int v0a=a[0];
    int v0b=b[0];
    
    for(int i=1; i<N; i++){
        int v= max(v0, max(v0a, v0b));
        int va= max(v0, max(v0a, v0b))+a[i];
        int vb= v0+b[i];
        
        v0=v;
        v0a=va;
        v0b=vb;
    }
    
    
    return max(v0, max(v0a, v0b));
}

/*int main()
{
    int n;
    FILE *in = stdin, *out = stdout;
    assert(fscanf(in, "%d", &n) == 1);

    int *a = (int*)calloc(n, sizeof(int));
    int *b = (int*)calloc(n, sizeof(int));

    for(int i=0; i<n; i++){
      assert(fscanf(in, "%d", a + i) == 1);
      assert(fscanf(in, "%d", b + i) == 1);
    }

    int answ = tempo_massimo(n, a, b);
    fprintf(out, "%d\n", answ);

    free(a);
    free(b);

    fclose(in);
    fclose(out);

    return EXIT_SUCCESS;
}
*/