#include <cstdio>
#include <string>
#include <vector>

void solution();

int main()
{
#define FNAME "password"
    freopen(FNAME ".in", "r", stdin);
    freopen(FNAME ".out", "w", stdout);
#undef FNAME

    solution();

    return 0;
}

inline void solution()
{
    const int len = 100000;
    char s[len];
    int n;

    scanf("%d", &n);
    scanf("%s", s);

    std::vector<std::string> result;

    std::string str(&s[0], 1);

    for (int i = 1; i < n; i++)
    {
        if (s[i - 1] == s[i])
        {
            str += s[i];
        }
        else
        {
            result.push_back(str);
            str.clear();
            str.assign(&s[i], 1);
        }
    }
    result.push_back(str);

    int max = 1;
    const size_t size = result.size();

    for (int i = 0; i < size; i++)
    {
        if (result[i].size() > max)
        {
            max = result[i].size();
        }
    }

    int count = 0;

    for (int i = 0; i < size; i++)
    {
        if (result[i].size() == max)
        {
            count++;
        }
    }

    printf("%d\n", count);

    for (int i = 0; i < size; i++)
    {
        if (result[i].size() == max)
        {
            printf("%s\n", result[i].c_str());
        }
    }
}