#include<stdio.h>

#define max(a,b) ( (a) > (b) ? (a) : (b) )

int n,sum[3][101],temp,ans;

int main(void){
	register int i,j;
	scanf("%d",&n);
	for(i=1;i<=2;i++)
		for(j=1;j<=n;j++)
			scanf("%d",&temp),
			sum[i][j]=sum[i][j-1]+temp;
	for(i=1;i<=n;i++)
		ans=max(ans,sum[2][n]+sum[1][i]-sum[2][i-1]);
	printf("%d\n",ans);
	return 0;
}