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线段树维护等差数列，结点维护首项+公差即可

#include <cstdio>

#include <cstring>

#include <algorithm>

using namespace std;

typedef long long ll;

const int maxn = ;

#define lson(x) ((x)<<1)

#define rson(x) (((x)<<1)|1)

int lc[maxn << ], rc[maxn << ], v[maxn << ];

ll nd[maxn << ], ad[maxn << ], s[maxn << ];

void pushup(int u);

void pushdown (int u);

inline int length(int u) {

    return rc[u] - lc[u] + ;

}

inline void change (int u, ll a) {

    v[u] = ;

    ad[u] = ;

    nd[u] = a;

    s[u] = a * length(u);

}

inline void maintain (int u, ll a, ll d) {

    if (v[u] && lc[u] != rc[u]) {

        pushdown(u);

        pushup(u);

    }

    v[u] = ;

    nd[u] += a;

    ad[u] += d;

    ll n = length(u);

    s[u] += a * n + (((n-) * n) / ) * d;

}

inline void pushup (int u) {

    s[u] = s[lson(u)] + s[rson(u)];

}

inline void pushdown (int u) {

    if (v[u]) {

        change(lson(u), nd[u]);

        change(rson(u), nd[u]);

        v[u] = nd[u] = ;

    } else if (nd[u] || ad[u]) {

        maintain(lson(u), nd[u], ad[u]);

        maintain(rson(u), nd[u] + length(lson(u)) * ad[u], ad[u]);

        nd[u] = ad[u] = ;

    }

}

void build (int u, int l, int r) {

    lc[u] = l;

    rc[u] = r;

    nd[u] = ad[u] = s[u] = ;

    if (l == r)

        return;

    int mid = (l + r) / ;

    build(lson(u), l, mid);

    build(rson(u), mid + , r);

    pushup(u);

}

void modify(int u, int l, int r, ll a, ll d) {

    if (l <= lc[u] && rc[u] <= r) {

        maintain(u, a + d * (lc[u] - l), d);

        return;

    }

    pushdown(u);

    int mid = (lc[u] + rc[u]) / ;

    if (l <= mid)

        modify(lson(u), l, r, a, d);

    if (r > mid)

        modify(rson(u), l, r, a, d);

    pushup(u);

}

void set(int u, int l, int r, ll a) {

    if (l <= lc[u] && rc[u] <= r) {

        change(u, a);

        return;

    }

    pushdown(u);

    int mid = (lc[u] + rc[u]) / ;

    if (l <= mid)

        set(lson(u), l, r, a);

    if (r > mid)

        set(rson(u), l, r, a);

    pushup(u);

}

ll query (int u, int l, int r) {

    if (l <= lc[u] && rc[u] <= r)

        return s[u];

    pushdown(u);

    ll ret = ;

    int mid = (lc[u] + rc[u]) / ;

    if (l <= mid)

        ret += query(lson(u), l, r);

    if (r > mid)

        ret += query(rson(u), l, r);

    pushdown(u);

    return ret;

}

int N;

int main () {

    while (~scanf("%d", &N)) {

        char op[];

        int l, r, x;

        build(, , );

        while (N--) {

            scanf("%s%d%d", op, &l, &r);

            if (op[] == 'A')

                modify(, l, r, , );

            else if (op[] == 'B')

                modify(, l, r, r - l + , -);

            else if (op[] == 'C') {

                scanf("%d", &x);

                set(, l, r, x);

            } else

                printf("%lld\n", query(, l, r));

        }

    }

    return ;

}