#include <iostream>
#include <vector>
#include <unordered_map>
#include <sstream>
#include <string>

using namespace std;

class Solution {
public:
    int majorityElement(vector<int>& arr) {
        int n = arr.size();
        if (n == 0) return -1;
        unordered_map<int, int> counts;
        for (int num : arr) {
            counts[num]++;
            if (counts[num] > n / 2) {
                return num;
            }
        }
        return -1;
    }
};

int main() {
    string line;
    if (getline(cin, line)) {
        if (line.empty()) {
            cout << -1 << endl;
            return 0;
        }
        stringstream ss(line);
        vector<int> arr;
        int num;
        while (ss >> num) {
            arr.push_back(num);
        }
        Solution sol;
        cout << sol.majorityElement(arr) << endl;
    }
    return 0;
}

import java.util.*;
import java.io.*;

public class Main {
    public static int majorityElement(int[] arr) {
        int n = arr.length;
        if (n == 0) return -1;
        Map<Integer, Integer> counts = new HashMap<>();
        for (int num : arr) {
            int count = counts.getOrDefault(num, 0) + 1;
            if (count > n / 2) {
                return num;
            }
            counts.put(num, count);
        }
        return -1;
    }

    public static void main(String[] args) throws IOException {
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        String line = br.readLine();
        if (line == null || line.trim().isEmpty()) {
            System.out.println(-1);
            return;
        }
        String[] parts = line.trim().split("\\s+");
        int[] arr = new int[parts.length];
        for (int i = 0; i < parts.length; i++) {
            arr[i] = Integer.parseInt(parts[i]);
        }
        System.out.println(majorityElement(arr));
    }
}

import sys

def majority_element(arr):
    n = len(arr)
    if n == 0:
        return -1
    counts = {}
    for num in arr:
        counts[num] = counts.get(num, 0) + 1
        if counts[num] > n // 2:
            return num
    return -1

def main():
    input_data = sys.stdin.read().strip()
    if not input_data:
        print(-1)
        return
    arr = list(map(int, input_data.split()))
    print(majority_element(arr))

if __name__ == '__main__':
    main()

const fs = require('fs');

function majorityElement(arr) {
    const n = arr.length;
    if (n === 0) return -1;
    const counts = new Map();
    for (const num of arr) {
        const count = (counts.get(num) || 0) + 1;
        if (count > Math.floor(n / 2)) {
            return num;
        }
        counts.set(num, count);
    }
    return -1;
}

function main() {
    const input = fs.readFileSync('/dev/stdin', 'utf-8').trim();
    if (!input) {
        console.log(-1);
        return;
    }
    const arr = input.split(/\s+/).map(Number);
    console.log(majorityElement(arr));
}

main();