import java.util.Scanner;
public class Main {
static int T ;
static int n ;
static int[] time ;
static int[] price ;
static int ans ;
static int[] dp;
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
T = sc.nextInt();
n = sc.nextInt();
time = new int[n+1];
price = new int[n+1];
dp = new int[T+1];
for (int i = 1; i <= n; i++) {
time[i] = sc.nextInt();
price[i] = sc.nextInt();
}
for (int i = 1; i <= n; i++) {
for (int j = T; j >= time[i]; j--) {
if (j >= time[i]) {
dp[j] = Math.max(dp[j], dp[j-time[i]]+price[i]);
// System.out.println(j + ":" + dp[T]);
}
}
}
System.out.println(dp[T]);
}
}
