A.cpp

#pragma comment(linker, "/STACK:16777216")
#include <iostream>
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <algorithm>
#include <vector>
#include <set>
#include <map>
#include <stack>
#include <queue>
#include <string>
#include <deque>
#include <complex>
#include <sstream>
#include <iomanip>

#define FOR(i,a,b) for(int i=(a),_b=(b); i<=_b; i++)
#define FORD(i,a,b) for(int i=(a),_b=(b); i>=_b; i--)
#define REP(i,a) for(int i=0,_a=(a); i<_a; i++)
#define ll long long
#define F first
#define S second
#define PB push_back
#define MP make_pair
using namespace std;

const double PI = acos(-1.0);

char s[200111], st[200111];
int top;

int main() {
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);
    gets(s);
    top = 0;
    int n = strlen(s);
    int i = 0;
    while (i < n) {
        if (top && s[i] == st[top]) {
            top--;
        }
        else {
            st[++top] = s[i];
        }
        i++;
    }
    FOR(i,1,top) cout << st[i];
    return 0;
}