using System;
class Program
{
static string removeAdjacentPair(string s) {
for (int i = 0; i < s.Length - 1; i++) {
if (s[i] == s[i + 1]) {
s = s.Remove(i, 2);
if (i != 0) i--;
}
}
return s;
}
static void Main() {
string s = "aabcccdeeffffgac";
s = removeAdjacentPair(s);
Console.Write(s);
}
}
/*
run:
bcdgac
*/