题解（243行）

# include <bits/stdc++.h>
typedef unsigned long long ull;

#define LL long long \

#define u1 u << 1 \

#define u2 u1 | 1 \

#define ef ((l + r) >> 1) \

using  namespace  std ;

bool cek(char c)
{
    if(c >= '0' && c <= '9')
    {
        return 1;
    }
    
    else
    {
        return 0;
    }
}

int r()
{
    short f = 1;
    int x = 0;
    
    char c;
    
    c = getchar();
    
    while (!chk(c))
    {
        if (c == '-')
        {
            f = -1;
        }
        
        c = getchar();
    }
    
    while (chk(c))
    {
        x = (x << 1) + (x << 3) + (c ^ (3 << 4));
        
        c = getchar();
    }
    
    x *= f;
    
    return x;
}

void w(int x)
{
    if (x == 0)
    {
        putchar('0');
        
        return;
    }
    
    w(x / 10);
    
    char aaa = 'A';
    aaa += (x % 10);
    
    putchar(aaa);
    
    return;
}

const int N = 1e5 + 3;

struct Node{
    LL sum;
    LL tag;
};

int n, m;
LL a[N];

Node seg[N << 2];

void pushup(int u)
{
    int aaa = seg[u1].sum;
    aaa += seg[u2].sum;
    
    seg[u].sum = aaa;
    
    return;
}

void pushdown(int u, int l, int r)
{
    LL &x = seg[u].tag;
    
    seg[u1].tag += x;
    seg[u2].tag += x;
    
    int mid = ef;
    LL aaa = mid - l + 1;
    LL aaa1 = r - mid;
    
    seg[u1].sum += 1ll * aaa * x;
    seg[u2].sum += 1ll * aaa1 * x;
    
    seg[u].tag = 0;
    
    return;
}

void build(int u, int l, int r)
{
    if (l == r)
    {
        seg[u].sum = a[l];
        seg[u].tag = 0;
        
        return;
    }
    
    int mid = ef;
    
    build(u1, l, mid);
    build(u2, mid + 1, r);
    
    pushup(u);
    
    return;
}

void modify(int u, int l, int r, int ql, int qr, int x)
{
    if(l == ql && r == qr)
    {
        int aaa = r - l + 1;
        
        seg[u].tag += x;
        seg[u].sum += 1ll * aaa * x;
        
        return;
    }
    
    pushdown(u, l, r);
    int mid = ef;
    
    if(qr <= mid)
    {
        modify(u1, l, mid, ql, qr, x);
    }
        
    else if(ql > mid)
    {
        modify(u2, mid + 1, r, ql, qr, x);
    }
        
    else
    {
        modify(u1, l, mid, ql, mid, x);
        modify(u2, mid + 1, r, mid + 1, qr, x);
    } 
    
    pushup(u);
    
    return;
}

LL query(int u, int l, int r, int ql, int qr)
{
    if (l == ql && r == qr)
    {
        return seg[u].sum;
    }  
    
    pushdown(u, l, r);
    int mid = ef;
    
    if (qr <= mid)
    {
        return query(u1, l, mid, ql, qr);
    }
    
    else if (ql > mid)
    {
        return query(u2, mid + 1, r, ql, qr);
    }
    
    else
    {
        int aaa = query(u1, l, mid, ql, mid);
        aaa += query(u2, mid + 1, r, mid + 1, qr);
        
        return aaa;
    }
}

int dfs(int a, int b)
{
    if (b == 0)
    {
        return a;
    }
    
    int aaa = dfs(a, b - 1);
    aaa ++;
    
    return aaa;
}

const int e3 = 1000;

int  main ( )
{
    int a, b;
    
    a = r();
    b = r();
    
    build(1, 1, e3);
    
    modify(1, 1, e3, 1, 1, a);
    modify(1, 1, e3, 2, 2, b);
    
    int aaa = query(1, 1, e3, 1, 2), aaa1 = dfs(a, b);
    
    if(aaa == aaa1)
    {
        int l = aaa, r = aaa1;
        int mid = ef;
        cout << ef;
    }
    
    cout << " ";
    cout << endl;
    
    return  0;
}