C++ :

#include <iostream>
#include <ctime>
#include <algorithm>
using namespace std;
int n,w;
int c[19];
int use[19];
int minn = 20;
bool cmp(int x,int y)
{
	return x>y;
}
void dfs(int pos,int tot)
{
	if(tot>minn)
		return ;
	if(pos == n+1)
	{
		minn = min(minn,tot);
		return ;
	}
	for(int i=1;i<=tot;i++)
	{
		if(c[pos] + use[i] <= w)
		{
			use[i] += c[pos];
			dfs(pos+1,tot);
			use[i] -= c[pos];
		}
	}
	use[tot+1] = c[pos];
	dfs(pos+1,tot+1);
	use[tot+1] = 0;
}
int main()
{
	cin>>n>>w;
	for(int i=1;i<=n;i++)
		cin>>c[i];
	// clock_t start = clock();
	sort(c+1,c+1+n,cmp);
	dfs(1,0);
	// clock_t end = clock();
	cout<<minn<<endl;
	// cout<<end-start<<endl;
	return 0;
}

Python :

# coding=utf-8
a,b=map(int,input().split())
n=0
cnt=0
for x in range(a):
    n=int(input())
    cnt+=n
if(int(cnt/b)==cnt/b):
    print(int(cnt/b))
else:
    print(int(cnt/b)+1)

  #include<bits/stdc++.h>
using namespace std;
const int N=25;
int c[N],n,w,a[N],res=N;
void dfs(int i,int j){
	if(i>n){
		res=min(res,j);
	}
	if(j>=res)return;
	for(int k=1;k<=j;k++){
		if(a[k]+c[i]>w)continue;
		a[k]+=c[i];
		dfs(i+1,j);
		a[k]-=c[i];
	}
	a[j+1]+=c[i];
	dfs(i+1,j+1);
	a[j+1]-=c[i];
}
int main(){
	cin>>n>>w;
	for(int i=1;i<=n;i++){
		cin>>c[i];
	}
	dfs(1,0);
	cout<<res;
	return 0;
}

```cpp
#include<bits/stdc++.h>
using namespace std;
int n,w;
int cat[20],cab[20],ans=20;
void dfs(int u,int k) {
//	if(u==n){//判定所有小猫都上车了 
//		ans=min(ans,k);//找最小的次数 
//		return;
//	}
	if(k>ans)return ;
	if(u==n){
		ans=k;
		return;
	}
	for(int i=0;i<k;i++){
		if(cab[i]+cat[u]<=w){
			cab[i]+=cat[u];
			dfs(u+1,k);
			cab[i]-=cat[u];
		}
	}
	cab[k]=cat[u];
	dfs(u+1,k+1);
	cab[k]-=cat[u];
}
int main(){ 
	cin>>n>>w;
	for(int i=0;i<n;i++)cin>>cat[i];
	sort(cat,n+cat,greater<int>());
	dfs(0,0);
	cout<<ans;
	return 0;
} 

#include<algorithm>
#include<iostream>
using namespace std;
const int MAXN = 114514;
int n,w,ans,c[MAXN],cab[MAXN];
void dfs(int now,int cnt) {
	if (cnt >= ans) {
		return ;
	}
	if (now == n + 1) {
		ans = min(ans,cnt);
		return ;
	}
	for (int i = 1;i <= cnt;i++) {
		if (cab[i] + c[now] <= w) {
			cab[i] += c[now];
			dfs(now + 1,cnt); 
			cab[i] -= c[now];
		}
	}
	cab[cnt + 1] = c[now];
	dfs(now + 1,cnt + 1);
	cab[cnt + 1] = 0;
}
int main() {
	cin >> n >> w;
	for (int i = 1;i <= n;i++) {
		cin >> c[i];
	}
	sort(c + 1,c + n + 1);
	reverse(c + 1,c + n + 1);
	ans = n;
	dfs(1,0);
	cout << ans << endl;
	return 0;
}

#include <bits/stdc++.h>
using namespace std;
const int N = 1e2 + 10;
const int mod = 1e9 + 7;
const int INF = 0x3f3f3f3f;
const long long LLINF = 0x3f3f3f3f3f3f3f3fLL;
int n, m, a[N], ans, sum[N];
void dfs(int u, int v){
	if(v >= ans) return;
	if(u == n){
		ans = v;
		return;
	}
	for(int i = 0 ; i < v ; i++){
		if(sum[i] + a[u] <= m){
			sum[i] += a[u];
			dfs(u + 1, v);
			sum[i] -= a[u];
		}
	}
	sum[v] = a[u];
	dfs(u + 1, v + 1);
	sum[v] = 0;
}
int main(){
	cin >> n >> m;
	ans = n;
	for(int i = 0 ; i < n ; i++){
		cin >> a[i];
	}
	sort(a, a + n, greater<int>());
	dfs(0, 0);
	cout << ans << endl;
	return 0;
}

11

# coding=utf-8
a,b=map(int,input().split())
n=0
cnt=0
for x in range(a):
    n=int(input())
    cnt+=n
if(int(cnt/b)==cnt/b):
    print(int(cnt/b))
else:
    print(int(cnt/b)+1)