#include <bits/stdc++.h>

inline int read() {
    int x = 0;
    register char ch = getchar();

    for (; !isdigit(ch); ch = getchar());

    for (; isdigit(ch); x = x * 10 + (ch & 15), ch = getchar());

    return x;
}
int st[20], TOP;
inline void write(int x) {
    if (!x)
        putchar(48);
    else {
        for (; x; st[++TOP] = x % 10, x /= 10);

        for (; TOP; putchar(st[TOP--] | 48));
    }
}
inline void writeln(int x) {
    write(x), putchar('\n');
}

const int MAXN = 55, MAXM = 410;

int n, m;
int S[MAXN], col0[MAXN], col1[MAXN], a[MAXN][MAXM];
std::vector <std::pair <int, int>> ans;
inline void move(int x, int y) {
    //printf("%d %d ",S[x],S[y]);
    assert(S[x] > 0);
    assert(S[y] < m);
    a[y][++S[y]] = a[x][S[x]], --S[x];
    ans.emplace_back(std::make_pair(x, y));
}
inline int size(int x) {
    return S[x];
}
inline int top(int x) {
    assert(S[x] > 0);
    return a[x][S[x]];
}
inline bool empty(int x) {
    return S[x] == 0;
}
inline bool full(int x) {
    return size(x) == m;
}
void solve(int L, int R, std::vector <int> vec) {
    if (L == R)
        return;

    int mid = (L + R) >> 1, len = R - L + 1;

    for (const auto &x : vec) {
        col0[x] = col1[x] = 0;

        for (int i = 1; i <= S[x]; ++i) {
            if (a[x][i] > mid)
                ++col1[x];
            else ++col0[x];

            assert(a[x][i] >= L && a[x][i] <= R);
        }
    }

#define col(x) (x > mid ? 1 : 0)

    for (int i = 0; i < len - 1; ++i) {
        int x = vec[i], y = vec[i + 1];
        int sx0 = col0[x], sx1 = col1[x], sy0 = col0[y], sy1 = col1[y];

        if (sx0 == 0 || sx1 == 0)
            continue;

        assert(sx0 + sx1 == m);
        assert(sy0 + sy1 == m);

        if (sx0 + sy0 > sx1 + sy1) {
            for (int i = 1; i <= sx0; ++i)
                move(y, n + 1);

            while (!empty(x))
                if (col(top(x)) == 0)
                    move(x, y);
                else
                    move(x, n + 1);

            assert(size(y) == m);
            assert(size(n + 1) == m);

            for (int i = 1; i <= m; ++i)
                move(y, x);

            for (int i = 1; i <= sx1; ++i)
                move(n + 1, y);

            for (int i = 1; i <= sx1; ++i)
                move(x, n + 1);

            assert(size(n + 1) == m);

            while (!empty(n + 1)) {
                if (full(x))
                    move(n + 1, y);
                else if (col(top(n + 1)) == 0)
                    move(n + 1, x);
                else
                    move(n + 1, y);
            }

            assert(size(x) == m);
            assert(size(y) == m);
            col0[x] = m, col1[x] = 0;
            col0[y] = sx0 + sy0 - m, col1[y] = sx1 + sy1;
        } else {
            for (int i = 1; i <= sx1; ++i)
                move(y, n + 1);

            while (!empty(x))
                if (col(top(x)) == 1)
                    move(x, y);
                else
                    move(x, n + 1);

            assert(size(y) == m);
            assert(size(n + 1) == m);

            for (int i = 1; i <= m; ++i)
                move(y, x);

            for (int i = 1; i <= sx0; ++i)
                move(n + 1, y);

            for (int i = 1; i <= sx0; ++i)
                move(x, n + 1);

            assert(size(n + 1) == m);

            while (!empty(n + 1)) {
                if (full(x))
                    move(n + 1, y);
                else if (col(top(n + 1)) == 1)
                    move(n + 1, x);
                else
                    move(n + 1, y);
            }

            assert(size(x) == m);
            assert(size(y) == m);
            col0[x] = 0, col1[x] = m;
            col0[y] = sx0 + sy0, col1[y] = sx1 + sy1 - m;
        }
    }

    std::vector <int> vec0, vec1;

    for (const auto &x : vec)
        if (col(top(x)) == 0)
            vec0.emplace_back(x);
        else
            vec1.emplace_back(x);

#undef col
    solve(L, mid, vec0), solve(mid + 1, R, vec1);
}

int main() { 
    n = read(), m = read();

    for (int i = 1; i <= n; ++i)
        S[i] = m;

    for (int i = 1; i <= n; ++i)
        for (int j = 1; j <= m; ++j)
            a[i][j] = read();

    std::vector <int> vec;

    for (int i = 1; i <= n; ++i)
        vec.emplace_back(i);

    solve(1, n, vec);
    writeln((int)ans.size());

    for (const auto &x : ans)
        write(x.first), putchar(' '), writeln(x.second);

    return 0;
}