import java.util.Scanner;

public class Main {
    static Scanner sc = new Scanner(System.in);
    static final int N = (int) (1e5 + 10), M = 320;
    static double[] w = new double[N], sum = new double[M], mulsum = new double[M], add = new double[M];
    static int n, t, len;
    public static void main(String[] args) throws Exception {
        n = sc.nextInt(); t = sc.nextInt();
        len = (int) Math.sqrt(n);

        for (int i = 1; i <= n; i++) {
            w[i] = sc.nextDouble();
            sum[get(i)] += w[i];
            mulsum[get(i)] += w[i] * w[i];
        }

        while (t-- > 0) {
            int op, l, r;
            op = sc.nextInt(); l = sc.nextInt(); r = sc.nextInt();
            if (op == 1) {
                double d = sc.nextDouble();
                modify(l, r, d);
            } else if (op == 2) {
                System.out.printf("%.4f\n", queryAvg(l, r));
            } else {
                System.out.printf("%.4f\n", queryVar(l, r));
            }
        }

    }

    // 算平方和
    static double queryVar(int l, int r) {
        double res = 0; // 平方和
        double m = 0; // 区间加和
        if (get(l) == get(r)) {
            for (int i = l; i <= r; i++) {
                double t = w[i] + add[get(i)];
                res += t * t;
                m += w[i] + add[get(i)];
            }
        } else {
            int i = l, j = r;
            while (get(i) == get(l)) {
                double t = w[i] + add[get(i)];
                res += t * t;
                m += w[i] + add[get(i)];
                i++;
            }
            while (get(j) == get(r)) {
                double t = w[j] + add[get(j)];
                res += t * t;
                m += w[j] + add[get(j)];
                j--;
            }
            for (int k = get(i); k <= get(j); k++) {
                res += mulsum[k] + 2 * sum[k] * add[k] + len * add[k] * add[k];
                m += sum[k] + add[k] * len;
            }
        }
        double length = r - l + 1;
        double avg = m / length; // res / length - avg^2
        return res / length - avg * avg;
    }

    // 算平均数
    static double queryAvg(int l, int r) {
        double res = 0;
        if (get(l) == get(r)) {
            for (int i = l; i <= r; i++) {
                res += w[i] + add[get(i)];
            }
        } else {
            int i = l, j = r;
            while (get(i) == get(l)) {
                res += w[i] + add[get(i)];
                i++;
            }
            while (get(j) == get(r)) {
                res += w[j] + add[get(j)];
                j--;
            }
            for (int k = get(i); k <= get(j); k++) {
                res += sum[k] + add[k] * len;
            }
        }
        return res / (double) (r - l + 1);
    }

    static void modify(int l, int r, double d) {
        if (get(l) == get(r)) {
            for (int i = l; i <= r; i++) {
                mulsum[get(i)] += 2.0 * d * w[i] + d * d;
                w[i] += d;
                sum[get(i)] += d;
            }
        } else {
            int i = l, j = r;
            while (get(i) == get(l)) {
                mulsum[get(i)] += 2.0 * d * w[i] + d * d;
                w[i] += d;
                sum[get(i)] += d;
                i++;
            }
            while (get(j) == get(r)) {
                mulsum[get(j)] += 2.0 * d * w[j] + d * d;
                w[j] += d;
                sum[get(j)] += d;
                j--;
            }
            for (int k = get(i); k <= get(j); k++) {
                add[k] += d;
            }
        }
    }

    static int get(int i) {
        return i / len;
    }

}