백준 1049

package baekjoon.그리디;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.util.Arrays;
import java.util.StringTokenizer;

class Main1049 {

   public static void main(String[] args) throws Exception {
      BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
      StringTokenizer st = new StringTokenizer(br.readLine());
      int N = Integer.parseInt(st.nextToken());
      int M = Integer.parseInt(st.nextToken());

      int[] a1 = new int[M];
      int[] a2 = new int[M];

      for (int i = 0; i < M; i++) {
         st = new StringTokenizer(br.readLine());
         a1[i] = Integer.parseInt(st.nextToken());
         a2[i] = Integer.parseInt(st.nextToken());
      }

      Arrays.sort(a1);
      Arrays.sort(a2);

      int ans = -1;

      ans = Math.min(((N / 6) + 1) * a1[0], Math.min((N * a2[0]), ((N / 6)) * a1[0] + (N % 6) * a2[0]));
      System.out.println(ans);

   }
}