#include <iostream>
#include <cstring>

using namespace std;
long long ans, cnt1, cnt2, V, n;
char s[100010];

int main()
{

  cin >> V >> s;
  n = strlen(s);

  for(int i= 0; i < n; i++)
  {
      if(s[i] == '2'){
          if(cnt1 + 2 * cnt2 + 2 <= V) cnt2++;
    }else
    {
        //s[i] = 1;
      if(cnt1 + 2 * cnt2 + 1 <= V) cnt1++;
      else if(cnt2>0) cnt2 --, cnt1++;
    }
    ans += cnt2+cnt1;
  }

     cout << ans << endl;

  return 0;
}

C++資料來源

public static void main(String[] args) {
    int num =1 ;
    Scanner scanner = new Scanner(System.in);
    int n = scanner.nextInt();
    String s = scanner.nextLine();

    int dayNum = 0;
    int totalNum = 0;
    int[] a = new int[s.length()];
    int number = 0;//背包现有药材占的份额
    for(int i = 1 ;i < s.length();i++) {
        int value = s.charAt(i) -48;
        int c = number + value;
            if (c <= n) {
                number += value;
                a[i] = value;
                dayNum++;
                totalNum += dayNum;
            }
            if (c > n && value == 1) {
                boolean flag = true;
                for (int j = 0; j < a.length; j++) {
                    if (a[j] == 2) {
                        a[j] = 1;
                        number = number-1;
                        flag = false;
                        totalNum += dayNum;
                        break;
                    }
                }
                if(flag)
                totalNum += dayNum;
            }
            if(value == 2 &&c > n){
                totalNum += dayNum;
            }

        }
    System.out.println(totalNum);
    }

java 資料來源