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                        ## Solution:
### - SỠdụng Vector Trong STL C++
### - Kết Hợp Vá»›i kỹ thuáºt Mảng cá»™ng dồn 
## My Code:
```cpp
#include <bits/stdc++.h>
using namespace std;
int main(){
	ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);	
	int n,q;
	cin >> n >> q;
	vector<int> v(n + 1);
	vector<long long> pre(n + 1);
	for(int i = 1;i <= n;i++){
		cin >> v[i];
		pre[i] = pre[i - 1] + v[i];
	}	
	while(q--){
		int c;
		cin >> c;
		if(c == 1){
			int x;
			cin >> x;
			v.push_back(x);
			pre.push_back(pre.back() + x);
		}
		if(c == 2){
			if(v.size()){
				v.pop_back();
				pre.pop_back();
			}
		}
		if(c == 3){
			int l,r;
			cin >> l >> r;
			cout << pre[r] - pre[l - 1] << "\n";
		}
	}
	return 0;
}
```