using Yorukatsu035.Questions;
using Yorukatsu035.Extensions;
using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;

namespace Yorukatsu035.Questions
{
    /// <summary>
    /// ABC153 E
    /// </summary>
    public class QuestionD : AtCoderQuestionBase
    {
        public override IEnumerable<object> Solve(TextReader inputStream)
        {
            var hn = inputStream.ReadIntArray();
            var hp = hn[0];
            var magicVariation = hn[1];

            var magics = new Magic[magicVariation];

            for (int i = 0; i < magicVariation; i++)
            {
                var ab = inputStream.ReadIntArray();
                var attack = ab[0];
                var mp = ab[1];

                magics[i] = new Magic(attack, mp);
            }

            var mps = new long[hp + 10000];
            for (int i = 1; i < mps.Length; i++)
            {
                mps[i] = 1L << 50;
            }

            for (int damage = 1; damage < mps.Length; damage++)
            {
                foreach (var magic in magics)
                {
                    var lastHP = damage - magic.Attack;
                    if (lastHP >= 0)
                    {
                        UpdateWhenSmall(ref mps[damage], mps[lastHP] + magic.MP);
                    }
                }
            }

            yield return mps.Skip(hp).Min();
        }

        public static void UpdateWhenSmall<T>(ref T value, T other) where T : IComparable<T>
        {
            if (other.CompareTo(value) < 0)
            {
                value = other;
            }
        }


        struct Magic
        {
            public int Attack { get; }
            public int MP { get; }

            public Magic(int attack, int mp)
            {
                Attack = attack;
                MP = mp;
            }
        }
    }
}


namespace Yorukatsu035
{
    class Program
    {
        static void Main(string[] args)
        {
            IAtCoderQuestion question = new QuestionD();    // 問題に合わせて書き換え
            var answers = question.Solve(Console.In);
            foreach (var answer in answers)
            {
                Console.WriteLine(answer);
            }
        }
    }
}

#region Base Classes

namespace Yorukatsu035.Questions
{

    public interface IAtCoderQuestion
    {
        IEnumerable<object> Solve(string input);
        IEnumerable<object> Solve(TextReader inputStream);
    }

    public abstract class AtCoderQuestionBase : IAtCoderQuestion
    {
        public IEnumerable<object> Solve(string input)
        {
            var stream = new MemoryStream(Encoding.Unicode.GetBytes(input));
            var reader = new StreamReader(stream, Encoding.Unicode);

            return Solve(reader);
        }

        public abstract IEnumerable<object> Solve(TextReader inputStream);
    }

}

#endregion

#region Extensions

namespace Yorukatsu035.Extensions
{
    internal static class TextReaderExtensions
    {
        internal static int ReadInt(this TextReader reader) => int.Parse(ReadString(reader));
        internal static long ReadLong(this TextReader reader) => long.Parse(ReadString(reader));
        internal static double ReadDouble(this TextReader reader) => double.Parse(ReadString(reader));
        internal static string ReadString(this TextReader reader) => reader.ReadLine();

        internal static int[] ReadIntArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(int.Parse).ToArray();
        internal static long[] ReadLongArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(long.Parse).ToArray();
        internal static double[] ReadDoubleArray(this TextReader reader, char separator = ' ') => ReadStringArray(reader, separator).Select(double.Parse).ToArray();
        internal static string[] ReadStringArray(this TextReader reader, char separator = ' ') => reader.ReadLine().Split(separator);
    }
}

#endregion

Measured memory_bytes: 13484