#![allow(unused_imports, unused_macros, dead_code)]

macro_rules! min {
    (.. $x:expr) => {{
        let mut it = $x.iter();
        it.next().map(|z| it.fold(z, |x, y| min!(x, y)))
    }};
    ($x:expr) => ($x);
    ($x:expr, $($ys:expr),*) => {{
        let t = min!($($ys),*);
        if $x < t { $x } else { t }
    }}
}
macro_rules! max {
    (.. $x:expr) => {{
        let mut it = $x.iter();
        it.next().map(|z| it.fold(z, |x, y| max!(x, y)))
    }};
    ($x:expr) => ($x);
    ($x:expr, $($ys:expr),*) => {{
        let t = max!($($ys),*);
        if $x > t { $x } else { t }
    }}
}


macro_rules! ewriteln {
    ($($args:expr),*) => { let _ = writeln!(&mut std::io::stderr(), $($args),*); };
}
macro_rules! trace {
    ($x:expr) => { ewriteln!(">>> {} = {:?}", stringify!($x), $x) };
    ($($xs:expr),*) => { trace!(($($xs),*)) }
}
macro_rules! put {
    (.. $x:expr) => {{
        let mut it = $x.iter();
        if let Some(x) = it.next() { print!("{}", x); }
        for x in it { print!(" {}", x); }
        println!("");
    }};
    ($x:expr) => { println!("{}", $x) };
    ($x:expr, $($xs:expr),*) => { print!("{} ", $x); put!($($xs),*) }
}

const M: i64 = 1_000_000_007;

#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, Copy, Debug)]
enum HypInt {
    NegInf, Real(i64), Inf
}
use HypInt::{Real, NegInf, Inf};
use std::ops::{Add, Sub, Neg};
impl Add for HypInt {
    type Output = Self;
    fn add(self, rhs: HypInt) -> HypInt {
        match (self, rhs) {
            (Real(x), Real(y)) => Real(x + y),
            (Inf, _) => Inf,
            (_, Inf) => Inf,
            _ => NegInf,
        }
    }
}
impl Sub for HypInt {
    type Output = Self;
    fn sub(self, rhs: HypInt) -> HypInt {
        match (self, rhs) {
            (Real(x), Real(y)) => Real(x - y),
            (Inf, _) => Inf,
            (_, Inf) => NegInf,
            (NegInf, _) => NegInf,
            (_, NegInf) => Inf,
        }
    }
}
impl Neg for HypInt {
    type Output = Self;
    fn neg(self) -> HypInt {
        match self {
            Inf => NegInf,
            NegInf => Inf,
            Real(x) => Real(-x),
        }
    }
}
fn main() {
    let mut sc = Scanner::new();
    let h: usize = sc.cin();
    let n: usize = sc.cin();

    let mut memo = vec![Inf; h + 10001];
    memo[0] = Real(0);

    let ps: Vec<_> = (0..n).map(|_| {
        let a: usize = sc.cin();
        let b: i64 = sc.cin();
        (a, b)
        }).collect();

    for j in 0..h {
        for &(a, b) in ps.iter() {
            if j + a < h + 10001 {
                memo[j + a] = min!(memo[j+a], memo[j] + Real(b));
            }
        }
    }
    let mut ans = 0;
    for i in h..h+10001 {
        if let Real(a) = memo[i] {
            if ans == 0 {
                ans = a;
            } else {
                ans = min!(ans, a);
            }
        }
    }

    put!(ans);
}

use std::io::{self, Write};
use std::str::FromStr;
use std::collections::VecDeque;

struct Scanner { stdin: io::Stdin, buffer: VecDeque<String>, }
impl Scanner {
    fn new() -> Self { Scanner { stdin: io::stdin(), buffer: VecDeque::new() } }
    fn cin<T: FromStr>(&mut self) -> T {
        while self.buffer.len() == 0 {
            let mut line = String::new();
            let _ = self.stdin.read_line(&mut line);
            for w in line.split_whitespace() {
                self.buffer.push_back(String::from(w));
            }
        }
        self.buffer.pop_front().unwrap().parse::<T>().ok().unwrap()
    }
    fn chars(&mut self) -> Vec<char> { self.cin::<String>().chars().collect() }
    fn vec<T: FromStr>(&mut self, n: usize) -> Vec<T> { (0..n).map(|_| self.cin()).collect() }
}


Measured memory_bytes: 4352