#include <bits/stdc++.h>
using namespace std;
const int MX = (int)1e6 + 17;
const int MOD = (int)1e9 + 7;
const long long oo = (long long)1e18 + 7;
const int INF = (int)999999999;
const int N = (int)1e5 + 17;
const int di[4] = {-1, 0, 1, 0};
const int dj[4] = {0, 1, 0, -1};
inline long long IN() {
  long long x = 0, ch = getchar(), f = 1;
  while (!isdigit(ch) && (ch != '-') && (ch != EOF)) ch = getchar();
  if (ch == '-') {
    f = -1;
    ch = getchar();
  }
  while (isdigit(ch)) {
    x = (x << 1) + (x << 3) + ch - '0';
    ch = getchar();
  }
  return x * f;
}
inline void OUT(long long x) {
  if (x < 0) putchar('-'), x = -x;
  if (x >= 10)
    OUT(x / 10), putchar(x % 10 + '0');
  else
    putchar(x + '0');
}
int n, L, R;
string s, l, r;
int main() {
  cin >> n >> s;
  l = s.substr(0, n);
  r = s.substr(n, (int)s.size());
  sort(l.begin(), l.end()), sort(r.begin(), r.end());
  for (int i = 0; i < n; i++) {
    if (l[i] > r[i]) L++;
    if (l[i] < r[i]) R++;
  }
  if (max(L, R) == n)
    cout << "YES";
  else
    cout << "NO";
  return 0;
}
