D.cpp

#include<bits/stdc++.h>
using namespace std;

#define SET(t,v) memset((t), (v), sizeof(t))
#define ALL(x) x.begin(), x.end()
#define UNIQUE(c) (c).resize( unique( ALL(c) ) - (c).begin() )

#if __cplusplus > 199711L
#define ItREP(it,c) for(auto it = (c).begin(); it!= (c).end(); it++)
#define REP(i,n) for(decltype(n) i=0;i<n;i++)
#define IREP(in,i,n) for(decltype(n) i=in;i<n;i++)
#else
#define ItREP(it,c) for(typeof((c).begin()) it = (c).begin(); it!= (c).end(); it++)
#define REP(i,n) for(typeof(n) i=0;i<n;i++)
#define IREP(in,i,n) for(typeof(n) i=in;i<n;i++)
#endif

#define IN(a,b) ( (b).find(a) != (b).end())
#define PB push_back
#define MP make_pair

typedef long long ll;
typedef long double LD;
typedef pair<int,int> pii;

#ifdef DEBUG
#define dbg(msg) msg
#define dbgp(msg) cerr << msg << endl;
#define var(v) cerr << #v << " = " << v << endl;
#else
#define dbg(msg) //msg
#define dbgp(msg) //cerr << msg << endl;
#define var(v) //cerr << #v << " = " << v << endl;
#endif


string astr,bstr;

int piisize(pii p){
    return p.second - p.first;
}

bool piieq(pii a,pii b){
    if(piisize(a) != piisize(b)){
        return false;
    }

    int i=0;
    int size = piisize(a);
    REP(i,size){
        if(astr[a.first+i] != bstr[b.first+i]) return false;
    }
    return true;
}

bool equavalent(pii a, pii b){
    if(piieq(a,b)){
        return true;
    }
    if(piisize(a) == piisize(b) && piisize(a) % 2 == 0){
        pii a1 = MP(a.first, (a.first+a.second)/2);
        pii a2 = MP((a.first+a.second)/2, a.second);
        pii b1 = MP(b.first, (b.first+b.second)/2);
        pii b2 = MP((b.first+b.second)/2, b.second);

        bool ans = ( equavalent(a1,b1) && equavalent(a2,b2) ) || 
            ( equavalent(a2,b1) && equavalent(a1,b2) );
        return ans;
    }else{
        return false;
    }
}

int main(int argv, char** argc){
    cin.sync_with_stdio(0);
    cin >> astr >> bstr;

    if( equavalent(MP(0,astr.size()), MP(0,bstr.size())) ){
        printf("YES\n");
    }else{
        printf("NO\n");
    }

    return 0;
}