function Main(input) {
    const lines = input.split(/\n/);
    const n = Number(lines[0]);
    var area = [];
    lines.slice(1).forEach(line=>{
        area.push(
            line.split(/\s/).map(str=>{return Number(str)})
        );
    });
    var count = 0;
    for(var down = 0; down < n; down++){
        var sum = 0;
        for(var i = 0; i < n; i++){
            if(i <= down){
                sum += area[0][i];
            }
            if(i >= down){
                sum += area[1][i];
            }
        }
        count = Math.max(count,sum);
    }
    console.log(count);
}
Main(require('fs').readFileSync('/dev/stdin', 'utf8'));