1 #include <cstdio>

 2 #include <cstring>

 3 #include <algorithm>

 4 #include <string>

 5 #include <vector>

 6 #include <map>

 7 #include <cmath>

 8 #include <iostream>

 9 #include <random>

10 #include <ctime>

11 using namespace std;

12 typedef long long ll;

13 const int maxn = 1e6 + 10;

14 char ans[11];

15 bool ask(ll l, ll r)

16 {

17     //printf("$$$$");

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

19     fflush(stdout);

20     scanf("%s", ans);

21     if(ans[0] == 'Y')

22     {

23         if(l == r) exit(0);

24         else return 1;

25     }

26     else return 0;

27 }

28 int na[maxn];

29 int main()

30 {

31     ll n, k;

32     srand(time(NULL));

33     scanf("%lld %lld", &n, &k);

34     ll l = 1, r = n;

35     while(l <= r)

36     {

37         ll mid = l + (r - l) / 2;

38         if(ask(l, mid))

39         {

40             r = mid;//注意这点，我的理解是mid可能就是我们要找的点，如果用常规写法r=mid-1会把这个点跳过去

41             //但我试了几个样例，发现在区间不断变化且有随机数的情况下，及时r=mid-1也能找到答案。。

42         }

43         else

44         {

45             l = mid + 1;

46         }

47             l = max(1ll, l - k);

48             r = min(n, r + k);

49             mid = l + rand()%(r - l + 1);

50             ask(mid, mid);

51             l = max(1ll, l - k);

52             r = min(n, r + k);

53     }

54     return 0;

55 }