import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {
    public static void main(String [] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String[] split = br.readLine().split(" ");
        int r = Integer.parseInt(split[0]);
        int n = Integer.parseInt(br.readLine());
        int res = 0;
        for(int i = 0 ;i < n ;i++){
            String[] split1 = br.readLine().split(" ");
            int a = Integer.parseInt(split1[0]);
            int b = Integer.parseInt(split1[1]);
            if (a==0 || a==1){
                res+=b;
            }else if (a==2){
                res+=b + r;
            }
        }
        System.out.println(res);
    }
}