"use strict";
    
const main = arg => {
    arg = arg.trim().split("\n");
    const N     = ~~arg[0];
    const table = arg.slice(1, 3).map(n=>n.split(" ").map(l=>~~l));
    
    let cnt = 0;
    
    for(let down=0; down<N; down++) {
        let sum = 0;
        
        for(let i=0; i<N; i++) {
            if(i <= down) {
                sum += table[0][i];
            }
            if(i >= down) {
                sum += table[1][i];
            }
        }
        
        cnt = Math.max(cnt, sum);
    }
    
    console.log(cnt);
}
main(require('fs').readFileSync('/dev/stdin', 'utf8'));