fn main() {
    proconio::input! {
        n: usize,
        a: [i64; n],
    }
    let total_diff = a[0]
        + a.iter()
            .zip(a.iter().skip(1))
            .map(|(x, y)| (y - x).max(0))
            .sum::<i64>();
    if total_diff <= n as i64 {
        println!("Yes");
    } else {
        println!("No");
    }
}