#include <iostream>
#include <bits/stdc++.h>
#define int long long
#define TASKNAME "bstsimple"
using namespace std;



struct bts{
    struct Node {
        Node *l , *r ;
        int val;
        Node(int x) {
            l = nullptr;
            r = nullptr;
            val = x;
        }
    };

    Node *root = nullptr;

    bool exists(int x) {
        Node *cur = root;
        while (cur) {
            if (x > cur->val) {
                cur = cur->r;
            } else if (x < cur->val) {
                cur = cur->l;
            } else {
                return true;
            }
        }
        return false;
    }


    void push(int x) {
        if (root == nullptr) {
            root = new Node(x);
            return;
        }
        Node *cur = root;
        while (cur) {
            if (x > cur->val) {
                if (cur->r == nullptr) {
                    cur->r = new Node(x);
                    return;
                }
                cur = cur->r;
            } else if (x < cur->val) {
                if (cur->l == nullptr) {
                    cur->l = new Node(x);
                    return;
                }
                cur = cur->l;
            } else {
                return;
            }
        }
        return;
    }


    void rem(int x) {
        Node *to_delete = root;
        Node *parent = nullptr;
        bool left = false;
        while (to_delete) {
            if (x > to_delete->val) {
                parent = to_delete;
                left = false;
                to_delete = to_delete->r;
            } else if (x < to_delete->val) {
                parent = to_delete;
                left = true;
                to_delete = to_delete->l;
            } else {
                break;
            }
        }
        if (to_delete == nullptr || to_delete->val != x) return;
        if (to_delete->l != nullptr) {
            Node *r_node = to_delete->r;
            Node *temp = to_delete->l;
            while (temp->r != nullptr) {
                temp = temp->r;
            }
            temp->r = r_node;
            to_delete = to_delete->l;
        } else if (to_delete->l == nullptr) {
            to_delete = to_delete->r;
        }
        if (parent != nullptr) {
            if (left) {
                parent->l = to_delete;
            } else {
                parent->r = to_delete;
            }
        } else {
            root = to_delete;
        }
    }

    int next(int x) {
        if (root == nullptr) {
            return INT_MIN;
        }
        Node *cur = root;
        int ans = INT_MAX;
        while (cur) {
            if (x >= cur->val) {
                if (cur->r == nullptr) {
                    return ans;
                }
                cur = cur->r;
            } else if (x < cur->val) {
                ans = cur->val;
                if (cur->l == nullptr) {
                    return ans;
                }
                cur = cur->l;
            } else {
                return ans;
            }
        }
        return ans;
    }

    int prev(int x) {
        if (root == nullptr) {
            return INT_MIN;
        }
        Node *cur = root;
        int ans = INT_MIN;
        while (cur) {
            if (x > cur->val) {
                ans = cur->val;
                if (cur->r == nullptr) {
                    return ans;
                }
                cur = cur->r;
            } else if (x <= cur->val) {
                if (cur->l == nullptr) {
                    return ans;
                }
                cur = cur->l;
            } else {
                return ans;
            }
        }
        return ans;
    }
};


// #define DEV
int32_t main() {
    #ifndef DEV
        freopen(TASKNAME".in", "r", stdin);
        freopen(TASKNAME".out", "w", stdout);
    #endif
    string s;
    bts kek;
    while (cin >> s) {
        if (s == "insert") {
            int x; cin >> x;
            kek.push(x);
        }
        if (s == "delete") {
            int x; cin >> x;
            kek.rem(x);
        }
        if (s == "exists") {
            int x;
            cin >> x;
            if (kek.exists(x)) {
                cout << "true" << endl;
            } else {
                cout << "false" << endl;
            }
        }
        if (s == "next") {
            int x;
            cin >> x;
            int ans = kek.next(x);
            if (ans == INT_MIN || ans == INT_MAX) {
                cout << "none\n";
            } else {
                cout << ans << endl;
            }
        }
        if (s == "prev") {
            int x;
            cin >> x;
            int ans = kek.prev(x);
            if (ans == INT_MIN || ans == INT_MAX) {
                cout << "none\n";
            } else {
                cout << ans << endl;
            }
        }

    }