sumpow2_eu

#include <bits/stdc++.h>

using namespace std;
ifstream fin("sumpow2.in");
ofstream fout("sumpow2.out");
int n, v[]={1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768}, sm;
char ch, s[]="abcdefghijklmnop";
int main()
{
    while(fin>>ch)
        sm+=v[s[ch-'a']-'a'];
    while(sm != 0)
    {
        if(sm%2==1)
            fout<<s[n];
        sm /= 2;
        n++;
    }
    return 0;
}