#include <iostream>
#include <vector>
#include <algorithm>

using int64 = long long;

int64 n, m;
std::vector<std::pair<int64, int64>> deer, elves;

bool check(int64 k)
{
    int64 j = 1;

    for (int64 i = 1; i <= m; ++i)
    {
        if (j > k)
            continue;

        if (elves[j].first < deer[i].first && deer[i].first < elves[n - k + j].first)
            ++j;
    }

    return j > k;
}

int main()
{
    std::cin >> m >> n;

    deer.assign(m + 1, { -1, -1 });
    elves.assign(n + 1, { -1, -1 });

    for (int64 i = 1; i <= m; ++i)
    {
        std::cin >> deer[i].first;
        deer[i].second = i;
    }

    std::sort(deer.begin(), deer.end());

    for (int64 i = 1; i <= n; ++i)
    {
        std::cin >> elves[i].first;
        elves[i].second = i;
    }

    std::sort(elves.begin(), elves.end());

    int64 l = 0;
    int64 r = std::min(m, n / 2) + 1;
    int64 mid;

    while (r - l > 1)
    {
        mid = (l + r) / 2;
        if (check(mid))
            l = mid;
        else
            r = mid;
    }

    std::cout << l << '\n';
    int64 j = 1;

    for (int64 i = 1; i <= m; ++i)
    {
        if (j > l)
            continue;

        if (elves[j].first < deer[i].first && deer[i].first < elves[n - l + j].first)
        {
            std::cout << deer[i].second << ' ' << elves[j].second << ' ' << elves[n - l + j].second << '\n';
            ++j;
        }
    }
    return 0;
}