參考下面部落格的公式：

需要注意的是，輸入初始數列的時候要 add 兩次， L = R, add (L, x), add (R+1, -x)

#include <iostream>
#include <cstring>
#include <cstdio>

using namespace std;

typedef long long ll;
const int Maxn = 1e5+10;

ll d[Maxn],di[Maxn];
int n;

void add (int x, int y) {
    int tmp = x;
    while (x <= n) {
        d[x] += y;
        di[x] += (ll)tmp*y;
        x += x&(-x);
    }
}

ll sum (int x) {  
    ll ret = 0, ans2 = 0; int tmp = x;
    while (x > 0) {
        ret+= (tmp+1)*d[x]-di[x];
        x -= x&(-x);
    }
    return ret;
}

int main (void)
{
    int m, tmp;
    scanf ("%d%d", &n, &m);
    for (int i = 1; i <= n; ++i) {
        scanf ("%d", &tmp);
        add (i, tmp);  // 注意輸入初始值的時候需要 add兩次, 
        add (i+1, -tmp); // L = R = i,add (L, x),add (R+1, -x)
    }
    char op[2]; int L, R, val;
    while (m--) {
        scanf ("%s", op);
        if (!strcmp (op, "C")) {
            scanf ("%d%d%d", &L, &R, &val);
            add (L, val);
            add (R+1, -val);
        } else {
            scanf ("%d%d", &L, &R);
            printf ("%lld\n", sum (R)-sum(L-1));
        }
    }
    return 0;
}