#include <iostream>
#include <string>
#include <sstream>
#include <vector>
using namespace std;

//解析字符串为数组
vector<int> parseCSV(string& input) {
    vector<int> numbers;
    stringstream ss(input);
    string token;
    while (getline(ss, token, ',')) {
        // 将token转换为整数并添加到数组
        numbers.push_back(stoi(token));
    }
    return numbers;
}


int main() 
{
    string s;  //作为字符串接受后解析数据
    vector<int> nums;
    while (cin >> s)
    {nums = parseCSV(s);
    int i,j=0;
    i=nums.size();
    int a[i];
    for (int num : nums) 
    {
        a[j++] = num;
    }
    for(j=0 ; j<=i/2-1 ; j++)
    {
        cout << a[j] <<","<<a[i-j-1];
        if(j!=i/2-1) cout<<",";
    }
    //第二个链表翻转
    if( i%2==1&& i!=1) cout <<","<< a[i/2];
    else if(i%2==1) cout << a[i/2];
    }
    
}
// 64 位输出请用 printf("%lld")