#include <iostream>
#include<vector>
#include<math.h>
#include<algorithm>
#include <utility>
#pragma once
long long mm, nn;
std ::vector<std ::pair<int, int>> aa, bb;
long long ans[100000][3], otv = 0;
bool podh(long long now) {
    long long col = 0 , ii = 0;
    while (ii < mm) {
        if (aa[ii].first > bb[col].first && aa[ii].first < bb[nn - now + col].first) {
            ++col;
            if (col == now) {
                return 1;
            }
        }
        ++ii;
    }
    return 0;
}

int main() {
    std ::cin >> mm >> nn;
    for (long long ii = 0; ii < mm; ++ii) {
        long long now;
        std ::cin >> now;
        aa.push_back(std ::make_pair(now, ii + 1));
    }
    for (long long ii = 0; ii < nn; ++ii) {
        long long now;
        std ::cin >> now;
        bb.push_back(std ::make_pair(now, ii + 1));
    }
    std ::sort(aa.begin(), aa.end());
    std ::sort(bb.begin(), bb.end());
    long long lhs = -1, rhs = std ::min(nn / 2, mm), mid;
    while (rhs > lhs + 1) {
        mid = (lhs + rhs) / 2;
        if (podh(mid)) {
            lhs = mid;
        } else {
            rhs = mid;
        }
    }
    if (!podh(rhs)) {
        --rhs;
    }
    if (rhs == -1) {
        std ::cout << 0;
        return 0;
    }
    long long col = 0 , ii = 0;
    while (ii < mm) {
        if (col == rhs) {
            break;
        }
        if (aa[ii].first > bb[col].first && aa[ii].first < bb[nn - rhs + col].first) {
            ans[col][0] = aa[ii].second;
            ans[col][1] = bb[col].second;
            ans[col][2] = bb[nn - rhs + col].second;
            ++col;
        }
        ++ii;
    }
    std ::cout << rhs << std ::endl;
    for (long long ii = 0; ii < rhs; ++ii) {
        std ::cout << ans[ii][0] << " " << ans[ii][1] << " " << ans[ii][2] << std ::endl;
    }
    return 0;
}