E. Arithmetic Progression

 http://codeforces.com/contest/1114/problem/E

题意：交互题，60个询问等差数列最小值和公差；

思路：约30个询问最大值log1e9)，约30个随机询问得到数列；

总结：rang()等到随机数较小，有得到数值大的随机算法；

https://codeforces.com/blog/entry/61587

#include<bits/stdc++.h>
#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<iostream>
#include<algorithm>
#include<set>
#include<vector>
#include<queue>
#include<cmath>
#include<cstring>
#include<sstream>
#include<cstdio>
#include<ctime>
#include<random>
#include<chrono>
#include<map>
#include<stack>
#include<string>
using namespace std;

#define sfi(i) scanf("%d",&i)
#define pri(i) printf("%d\n",i)
#define sff(i) scanf("%lf",&i)
#define ll long long
#define mem(x,y) memset(x,y,sizeof(x))
#define INF 0x3f3f3f3f
#define eps 1e-6
#define PI acos(-1)
#define lowbit(x) ((x)&(-x))
#define zero(x) (((x)>0?(x):-(x))<eps)
#define fl() printf("flag\n")
ll gcd(ll a,ll b){while(b^=a^=b^=a%=b);return a;}
const int maxn=5e3+9;
const int mod=1e9+7;

template <class T>
inline void sc(T &ret)
{
    char c;
    ret = 0;
    while ((c = getchar()) < '0' || c > '9');
    while (c >= '0' && c <= '9')
    {
        ret = ret * 10 + (c - '0'), c = getchar();
    }
}

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

int Max=-1e9;
int n,q=60,d=0;
vector<int>id,ans;
void FindMax()
{
    int l=0,r=1e9;
    while(l<=r)
    {
        int mid=(l+r)/2;
        int f=0;
        cout<<"> "<<mid<<endl;
        fflush(stdout);
        q--;
        cin>>f;
        if(f) l=mid+1;
        else r=mid-1,Max=mid;
    }
}

void FindD()
{
    int Range=n;
    while(q>0&&Range>0)
    {
        int index=rng()%Range;
        cout<<"? "<<id[index]<<endl;
        fflush(stdout);
        int k;
        cin>>k;
        ans.push_back(k);
        Range--;
        q--; 
        swap(id[index],id[Range]);//已经询问的不要了
    }
    sort(ans.begin(),ans.end());
    if(ans.back()!=Max) ans.push_back(Max);
    for(int i=1;i<ans.size();i++)
    {
        d=__gcd(d,ans[i]-ans[i-1]);
    }
}
int main()
{
    cin>>n;
    id.resize(n);
    for(int i=0;i<n;i++)
    {
        id[i]=i+1;
    }
    FindMax();
    FindD();
    cout<<"! "<<Max-(n-1)*d<<" "<<d<<endl;
    fflush(stdout);
    return 0;
}