区间修改，单点查询的树状数组

#include <bits/stdc++.h>
#define CLOSE ios::sync_with_stdio(false);cin.tie(0);cout.tie(0)
#define endl "\n"
typedef long long LL;
const int N = 1e6 + 10, M = N, mod = 1e9 + 7;
using namespace std;
int a[N], b[N], n, q;
LL  t[N];
int lowbit(int x) {return x & -x;}
void add(int x, int c){
    for(int i = x; i <= n; i += lowbit(i)){
        t[i] += c;
    }
}
LL getsum(int x){
    LL sum = 0;
    for(int i = x; i; i -= lowbit(i)){
        sum += t[i];
    }
    return sum;
}
int main()
{
    CLOSE;
    cin >> n >> q;
    for(int i = 1; i <= n; i ++){
        cin >> a[i];
    }
    for(int i = 1; i <= n; i ++){
        b[i] = a[i] - a[i - 1];
        add(i, b[i]);
    }
    while(q --){
        int op;
        cin >> op;
        if(op == 1){
            int l, r, k;
            cin >> l >> r >> k;
            add(r + 1, -k), add(l, k);
        } else{
            int k;
            cin >> k;
            cout << getsum(k)<< endl;
        }
    }
    return 0;
}