using System;
using System.Linq;
using System.Diagnostics;
using System.Collections.Generic;
using Debug = System.Diagnostics.Debug;
using StringBuilder = System.Text.StringBuilder;
using System.Numerics;
using Number = System.Int64;
using Point = System.Numerics.Complex;
using CHT = Optimization.SimpleCHT;
namespace Program
{
    public class Solver
    {
        public void Solve()
        {
            var n = sc.Integer();
            var a = sc.Long(n).Sum();
            IO.Printer.Out.WriteLine(a - sc.Long());

        }

        public IO.StreamScanner sc = new IO.StreamScanner(Console.OpenStandardInput());
        static T[] Enumerate<T>(int n, Func<int, T> f) { var a = new T[n]; for (int i = 0; i < n; ++i) a[i] = f(i); return a; }
        static public void Swap<T>(ref T a, ref T b) { var tmp = a; a = b; b = tmp; }
    }
}

#region main
static class Ex
{
    static public string AsString(this IEnumerable<char> ie) { return new string(System.Linq.Enumerable.ToArray(ie)); }
    static public string AsJoinedString<T>(this IEnumerable<T> ie, string st = " ") { return string.Join(st, ie); }
    static public void Main()
    {
        var solver = new Program.Solver();
        solver.Solve();
        Program.IO.Printer.Out.Flush();
    }
}
#endregion
#region Ex
namespace Program.IO
{
    using System.IO;
    using System.Text;
    using System.Globalization;
    public class Printer : StreamWriter
    {
        static Printer() { Out = new Printer(Console.OpenStandardOutput()) { AutoFlush = false }; }
        public static Printer Out { get; set; }
        public override IFormatProvider FormatProvider { get { return CultureInfo.InvariantCulture; } }
        public Printer(System.IO.Stream stream) : base(stream, new UTF8Encoding(false, true)) { }
        public Printer(System.IO.Stream stream, Encoding encoding) : base(stream, encoding) { }
        public void Write<T>(string format, T[] source) { base.Write(format, source.OfType<object>().ToArray()); }
        public void WriteLine<T>(string format, T[] source) { base.WriteLine(format, source.OfType<object>().ToArray()); }
    }
    public class StreamScanner
    {
        public StreamScanner(Stream stream) { str = stream; }
        public readonly Stream str;
        private readonly byte[] buf = new byte[1024];
        private int len, ptr;
        public bool isEof = false;
        public bool IsEndOfStream { get { return isEof; } }
        private byte read()
        {
            if (isEof) return 0;
            if (ptr >= len) { ptr = 0; if ((len = str.Read(buf, 0, 1024)) <= 0) { isEof = true; return 0; } }
            return buf[ptr++];
        }
        public char Char() { byte b = 0; do b = read(); while ((b < 33 || 126 < b) && !isEof); return (char)b; }

        public string Scan()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b >= 33 && b <= 126; b = (char)read())
                sb.Append(b);
            return sb.ToString();
        }
        public string ScanLine()
        {
            var sb = new StringBuilder();
            for (var b = Char(); b != '\n'; b = (char)read())
                if (b == 0) break;
                else if (b != '\r') sb.Append(b);
            return sb.ToString();
        }
        public long Long()
        {
            if (isEof) return long.MinValue;
            long ret = 0; byte b = 0; var ng = false;
            do b = read();
            while (b != 0 && b != '-' && (b < '0' || '9' < b));
            if (b == 0) return long.MinValue;
            if (b == '-') { ng = true; b = read(); }
            for (; true; b = read())
            {
                if (b < '0' || '9' < b)
                    return ng ? -ret : ret;
                else ret = ret * 10 + b - '0';
            }
        }
        public int Integer() { return (isEof) ? int.MinValue : (int)Long(); }
        public double Double() { var s = Scan(); return s != "" ? double.Parse(s, CultureInfo.InvariantCulture) : double.NaN; }
        private T[] enumerate<T>(int n, Func<T> f)
        {
            var a = new T[n];
            for (int i = 0; i < n; ++i) a[i] = f();
            return a;
        }

        public char[] Char(int n) { return enumerate(n, Char); }
        public string[] Scan(int n) { return enumerate(n, Scan); }
        public double[] Double(int n) { return enumerate(n, Double); }
        public int[] Integer(int n) { return enumerate(n, Integer); }
        public long[] Long(int n) { return enumerate(n, Long); }
    }
}
#endregion


#region CHT
namespace Optimization
{
    using N = System.Int64;
    struct L
    {
        internal N a, b;
        /// <summary>
        /// u*x+v
        /// </summary>
        public L(N u, N v) : this() { a = u; b = v; }

        /// <summary>
        /// F(x)=a*x+b
        /// </summary>
        public N F(int x) { return a * x + b; }
    }
    /// <summary>
    /// 追加される直線の傾きが単調減少
    /// </summary>
    public class SimpleCHT
    {
        int s, t;
        List<L> deq = new List<L>();
        /// <summary>
        /// ax+b を追加
        /// aは単調減少でないとダメ,ならしO(1)
        /// </summary>
        public void AddLine(N a, N b)
        {
            var l = new L(a, b);
            while (s + 1 < t && check_slow(deq[t - 2], deq[t - 1], l)) { t--; deq.RemoveAt(t); }
            deq.Add(l);
            t++;
        }
        /// <summary>
        /// xが単調増加のときのみ使ってよい,ならしO(1)
        /// </summary>
        public N Get(int x)
        {
            while (s + 1 < t && deq[s].F(x) >= deq[s + 1].F(x)) s++;
            return deq[s].F(x);
        }

        /// <summary>
        /// xが単調増加でないときでも使える,O(logN)
        /// </summary>
        /// <param name="x"></param>
        /// <returns></returns>
        public N Query(int x)
        {
            var l = s - 1; var h = t - 1;
            while (l + 1 < h)
            {
                var m = (l + h) / 2;
                if (isR_fast(deq[m], deq[m + 1], x)) l = m;
                else h = m;
            }
            return deq[h].F(x);

        }

        /// <summary>
        /// ax,bが小さい
        /// </summary>
        private bool isR_fast(L l1, L l2, int x)
        {
            return (l1.b - l2.b) >= x * (l2.a - l1.a);
        }
        /// <summary>
        /// ax,bが大きい
        /// </summary>
        private bool isR_slow(L l1, L l2, int x)
        {
            BigInteger b1 = l1.b, b2 = l2.b;
            BigInteger a1 = l1.a, a2 = l2.a;
            return (b1 - b2) >= x * (a2 - a1);
        }

        /// <summary>
        /// a*bが小さい
        /// </summary>
        private bool check_fast(L l1, L l2, L l3)
        {
            return (l2.a - l1.a) * (l3.b - l2.b) >= (l2.b - l1.b) * (l3.a - l2.a);
        }
        /// <summary>
        /// a*bが大きい
        /// </summary>
        private bool check_slow(L l1, L l2, L l3)
        {
            BigInteger a1 = l1.a, a2 = l2.a, a3 = l3.a;
            BigInteger b1 = l1.b, b2 = l2.b, b3 = l3.b;

            return (a2 - a1) * (b3 - b2) >= (b2 - b1) * (a3 - a2);
        }
    }
}
#endregion