import java.util.Scanner;
public class Main {
public static void main(String[] args) {
Scanner sc = new Scanner(System.in);
int t = sc.nextInt();
int m = sc.nextInt();
int[] dp = new int[t + 1];
while (m-- != 0) {
int weight = sc.nextInt();
int value = sc.nextInt();
for (int i = t; i >= weight; i--) {
dp[i] = Math.max(dp[i], dp[i - weight] + value);
}
}
System.out.println(dp[t]);
}
}

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