为啥WA了，样例可都过了呀

#include<bits/stdc++.h>
#define int long long
#define endl '\n'
const int N=2e5+10;
using namespace std;
int n,q;
int a[N];
signed main() {
    cin>>n;
    for(int i=1;i<=n;i++){
    	cin>>a[i];
	}
	cin>>q;
	while(q--){
		int op;cin>>op;
		if(op==1){
			int k,sum=n;
			cin>>k;
			while(sum--){
				a[sum]=k;
			}
		}
		if(op==2){
			int xb,k;
			cin>>xb>>k;
			a[xb]=a[xb]+k;
		}
		if(op==3){
			int xb;
			cin>>xb;
			cout<<a[xb]<<endl;
		}
	}
    return 0;
}