func_code_string: #include <bits/stdc++.h>   using namespace std;   template <class T>   void _R(T &x) {     cin >> x;   }   void _R(int &x) { scanf( %d , &x); }   void _R(long long &x) { scanf( %lld , &x); }   void _R(double &x) { scanf( %lf , &x); }   void _R(char &x) { scanf(  %c , &x); }   void _R(char *x) { scanf( %s , x); }   void R() {}   template <class T, class... U>   void R(T &head, U &...tail) {     _R(head);     R(tail...);   }   template <class T>   void _W(const T &x) {     cout << x;   }   void _W(const int &x) { printf( %d , x); }   void _W(const long long &x) { printf( %lld , x); }   void _W(const double &x) { printf( %.16f , x); }   void _W(const char &x) { putchar(x); }   void _W(const char *x) { printf( %s , x); }   template <class T, class U>   void _W(const pair<T, U> &x) {     _W(x.first);     putchar(   );     _W(x.second);   }   template <class T>   void _W(const vector<T> &x) {     for (auto i = x.begin(); i != x.end(); _W(*i++))       if (i != x.cbegin()) putchar(   );   }   void W() {}   template <class T, class... U>   void W(const T &head, const U &...tail) {     _W(head);     putchar(sizeof...(tail) ?     :   n );     W(tail...);   }   int MOD = 1e9 + 7;   void ADD(long long &x, long long v) {     x = (x + v) % MOD;     if (x < 0) x += MOD;   }   const int SIZE = 1e6 + 10;   int lv[SIZE], lat[SIZE];   vector<int> e[SIZE];   int can[SIZE];   int AA;   void dfs0(int x, int lt, int v) {     lv[x] = v;     for (int y : e[x]) {       if (y == lt) continue;       lat[y] = x;       dfs0(y, x, v + 1);     }   }   int target;   int cnt(int x, int lt, int dd) {     if (!dd) {       target = x;       return 1;     }     int ret = 0;     for (int y : e[x]) {       if (y == lt) continue;       ret += cnt(y, x, dd - 1);     }     return ret;   }   int dp[SIZE];   int dfs2(int x, int lt, int dd) {     if (!dd) {       dp[x] = can[x];       return -1;     }     dp[x] = 0;     for (int y : e[x]) {       if (y == lt) continue;       int now = dfs2(y, x, dd - 1);       if (now != -1) return now;       dp[x] += dp[y];       if (dp[x] >= (AA + 1) / 2) return x;     }     return -1;   }   void clear(int x, int lt, int dd) {     if (!dd) {       if (can[x]) {         can[x] = 0;         AA--;       }       return;     }     for (int y : e[x]) {       if (y == lt) continue;       clear(y, x, dd - 1);     }   }   void clear2(int x, int lt, int stop, int dd) {     if (x == stop) return;     if (!dd) {       if (can[x]) {         can[x] = 0;         AA--;       }       return;     }     for (int y : e[x]) {       if (y == lt) continue;       clear2(y, x, stop, dd - 1);     }   }   int find_answer() {     for (int i = (1); i <= (SIZE); ++i) {       if (can[i]) return i;     }     return -1;   }   int qq(int x, int dd) {     if (AA == 1) {       return find_answer();     }     if (!dd) return x;     int qx = dfs2(x, lat[x], dd);     if (qx != x) {       W( d , qx);       fflush(stdout);       int v;       R(v);       if (lv[qx] + v != lv[x] + dd) {         clear(qx, lat[qx], lv[x] + dd - lv[qx]);         qx = x;       } else {         clear2(x, lat[x], qx, dd);       }     }     if (AA == 1) {       return find_answer();     }     W( s , qx);     fflush(stdout);     int v;     R(v);     clear2(x, lat[x], v, dd);     return qq(v, dd - (lv[v] - lv[x]));   }   int main() {     int n;     R(n);     for (int i = (1); i < (n); ++i) {       int x, y;       R(x, y);       e[x].push_back(y);       e[y].push_back(x);     }     dfs0(1, 1, 0);     int now = 1, dd;     W( d , now);     fflush(stdout);     R(dd);     for (int i = (1); i <= (n); ++i) {       if (lv[i] == dd) {         can[i] = 1;         AA++;       }     }     W( ! , qq(1, dd));     return 0;   }   