namespace AtCoder;

#nullable enable

using System.Numerics;

static class Extensions
{
    public static T[] Repeat<T>(this int time, Func<T> F) => Enumerable.Range(0, time).Select(_ => F()).ToArray();

}

class AtCoder
{
    object? Solve()
    {
        var n = Int();
        var az = n.Repeat(() => Int() - 1);
        var sz = new int[n + 1];
        for (var i = 1; i <= n; i++) sz[i] = sz[i - 1] + az[i - 1];
        var m = az.Max();
        var u = (m + 1) * n * 2 + 1;
        var ans = (long)n * (n - 1) / 2 + 1;
        var mods = new int[u * 2];
        mods[u]++;
        for (var v = 0; v <= m; v++)
        {
            var lc = 0;
            for (var i = 1; i <= n; i++)
            {
                var k = sz[i] - v * i;
                var ku = k + u;
                if (az[i - 1] == v)
                {
                    ans -= lc;
                    lc++;
                }
                else
                {
                    lc = mods[ku];
                }
                mods[ku]++;
            }
            for (var i = 1; i <= n; i++)
            {
                var k = sz[i] - v * i;
                var ku = k + u;
                mods[ku]--;
            }
        }
        return ans;
    }

    public static void Main() => new AtCoder().Run();
    public void Run()
    {
        var res = Solve();
        if (res != null)
        {
            if (res is bool yes) res = yes ? "Yes" : "No";
            sw.WriteLine(res);
        }
        sw.Flush();
    }

    string[] input = Array.Empty<string>();
    int iter = 0;
    readonly StreamWriter sw = new(Console.OpenStandardOutput()) { AutoFlush = false };

    string String()
    {
        while (iter >= input.Length) (input, iter) = (Console.ReadLine()!.Trim().Split(' '), 0);
        return input[iter++];
    }
    T Input<T>() where T : IParsable<T> => T.Parse(String(), null);
    int Int() => Input<int>();
    void Out(object? x, string? separator = null)
    {
        separator ??= Environment.NewLine;
        if (x is System.Collections.IEnumerable obj and not string)
        {
            var firstLine = true;
            foreach (var item in obj)
            {
                if (!firstLine) sw.Write(separator);
                firstLine = false;
                sw.Write(item);
            }
        }
        else sw.Write(x);
        sw.WriteLine();
    }
}