function Main(s) {
  var s = s.split("\n");
  var n = s[0]*1;
  var a = s.slice(1, 3).map(e => e.split(" ").map(t => t*1));
  var b = new Array(n).fill(0);
  for(var i = 0; i < n; i++) {
    for(var j = i; j < n; j++) b[j] += a[0][i];
    for(var j = i; j < n; j++) {
      b[i] += a[1][j];
    }
  }
  max = 0;
  for(var i of b) max = Math.max(max, i);
  console.log(max);
}
Main(require("fs").readFileSync("/dev/stdin", "utf8"));