9 ЛКШ tle9

 #define pragma

#ifdef pragma
#pragma GCC optimize("Ofast,no-stack-protector,unroll-loops")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#endif // pragma

#include<bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long
#define all(x) begin(x), end(x)
#define pb push_back
#define x first
#define y second
#define int long long
#define zero(two) memset(two, 0, sizeof(two))

using namespace std;
using namespace __gnu_pbds;


typedef vector<int> vi;
typedef vector<bool> vb;
typedef pair<int, int> pii;
typedef long double ld;
typedef vector<vi> matrix;
template<typename T>
using kawaii_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = atan2(0, -1);

void seriy() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(10);
    #if _offline
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}

const int MAXN = 2e3 + 10;
const int INF = 1e18 + 7;
const int MAXLOG = 20;
const int MOD = 998244353;
const int BASE = 47;

signed main() {
    seriy();
    int n, q;
    cin >> n >> q;
    vector<ld> a(n);
    ld sum = 0;
    ld mx = 0;
    for(int i = 0; i < n; i++) {
        cin >> a[i];
        sum += a[i];
        mx = max(mx, a[i]);
    }
    sum -= a[0] / 2.;
    sum -= a[n - 1] / 2.;
    while(q--) {
        char t;
        cin >> t;
        if(t == 'Q') {
            int p;
            cin >> p;
            ld cur = 0;
            for(int i = 1; i < n; i++) {
                bool swp = 0;
                if(a[i - 1] > p && a[i] < p) {
                    swap(a[i], a[i - 1]);
                    swp = 1;
                }
                if(a[i - 1] < p && a[i] > p) {
                    cur += (a[i] - p) * (a[i] - p) / (2. * (a[i] - a[i - 1]));
                }
                else if(a[i - 1] >= p && a[i] >= p) {
                    cur += (a[i] + a[i - 1] - 2 * p) / 2.;
                }
                if(swp) {
                    swap(a[i], a[i - 1]);
                }
            }

            ld ans = mx * (n - 1) - sum + cur;
//            cerr << sum << '\n';
            ans += (p - mx) * (n - 1);
            cout << ans << '\n';
        }
        else {
            int pos;
            ld val;
            cin >> pos >> val;
            if(pos == 0 || pos == n - 1) {
                sum -= a[pos] / 2.;
                a[pos] = val;
                sum += a[pos] / 2.;
            }
            else {
                sum -= a[pos];
                a[pos] = val;
                sum += a[pos];
            }
            mx = 0;
            for(int i = 0; i < n; i++) {
                mx = max(mx, a[i]);
            }
        }
    }
    return 0;
}