cf 160B

#include<bits\stdc++.h>

using namespace std;

int main()
{
    int n, i;
    scanf("%d", &n);
    char s[2*n], s1[n], s2[n];
    scanf("%s", s);
    for(i = 0; i < n; i++) s1[i] = s[i];
    int j = i;
    for(i = 0; i < n; i++, j++) s2[i] = s[j];
    //cout << s1 << endl << s2 << endl;
    sort(s1, s1+n);
    sort(s2, s2+n);
    //cout << s1 << endl << s2 << endl;
    int sgrt = 1, sless = 1;
    for(i = 0; i < n; i++)
    {
        if(s1[i] <= s2[i])
        {
            sgrt = 0;
            break;
        }
    }
    for(i = 0; i < n; i++)
    {
        if(s2[i] <= s1[i])
        {
            sless = 0;
            break;
        }
    }

    if(sgrt == 1 || sless == 1) printf("YES\n");
    else printf("NO\n");
}