Codeforces Round #534 (Div. 2) D. Game with modulo 交互题

 

先二分一个区间，再在区间里面二分即可；

可以仔细想想，想明白很有意思的；

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstdlib>
#include<cstring>
#include<string>
#include<cmath>
#include<map>
#include<set>
#include<vector>
#include<queue>
#include<bitset>
#include<ctime>
#include<deque>
#include<stack>
#include<functional>
#include<sstream>
//#include<cctype>
//#pragma GCC optimize(2)
using namespace std;
#define maxn 200005
#define inf 0x7fffffff
//#define INF 1e18
#define rdint(x) scanf("%d",&x)
#define rdllt(x) scanf("%lld",&x)
#define rdult(x) scanf("%lu",&x)
#define rdlf(x) scanf("%lf",&x)
#define rdstr(x) scanf("%s",x)
typedef long long  ll;
typedef unsigned long long ull;
typedef unsigned int U;
#define ms(x) memset((x),0,sizeof(x))
//const long long int mod = 1e9 + 7;
#define Mod 1000000000
#define sq(x) (x)*(x)
#define eps 1e-4
typedef pair<int, int> pii;
#define pi acos(-1.0)
//const int N = 1005;
#define REP(i,n) for(int i=0;i<(n);i++)
typedef pair<int, int> pii;
inline ll rd() {
	ll x = 0;
	char c = getchar();
	bool f = false;
	while (!isdigit(c)) {
		if (c == '-') f = true;
		c = getchar();
	}
	while (isdigit(c)) {
		x = (x << 1) + (x << 3) + (c ^ 48);
		c = getchar();
	}
	return f ? -x : x;
}

ll gcd(ll a, ll b) {
	return b == 0 ? a : gcd(b, a%b);
}
int sqr(int x) { return x * x; }


/*ll ans;
ll exgcd(ll a, ll b, ll &x, ll &y) {
	if (!b) {
		x = 1; y = 0; return a;
	}
	ans = exgcd(b, a%b, x, y);
	ll t = x; x = y; y = t - a / b * y;
	return ans;
}
*/

string s;

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
	while (1) {
		cin >> s;
		if (s == "end") {
			return 0;
		}
		if (s == "start") {
			ll a = 1;
			for (; a < (1 << 30); a <<= 1) {
				cout << "?" << ' ' << a / 2 << ' ' << a << endl;
				fflush(stdout);
				cin >> s;
				if (s == "x") {
					break;
				}
			}
			// 区间 a/2~ a
			ll l = a / 2, r = a;
			while (l + 1 < r) {
				ll mid = (l + r) >> 1;
				cout << "?" << ' ' << mid << ' ' << l << endl;
				fflush(stdout);
				cin >> s;
				if (s == "x") {
					l = mid;
				}
				else r = mid;
			}
			cout << "!" << ' ' << r << endl;
			fflush(stdout);
		}
	}
}