#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
#define int ll
const int inf = 1e18;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef pair<int, int> p2;
#define rep(i, high) for (int i = 0; i < (high); i++)
#define repp(i, lo, high) for (int i = (lo); i < (high); i++)
#define repe(i, container) for (auto& i : container)
#define sz(x) ((int)(x).size())
#define all(x) begin(x), end(x)
inline void fast() { cin.tie(0)->sync_with_stdio(0); }
struct UF
{
vi par;
vi size;
UF(int n) : par(n), size(n, 1)
{
rep(i, n) par[i] = i;
}
int find(int x) { return par[x] == x ? x : par[x] = find(par[x]); }
void merge(int a, int b)
{
a = find(a), b = find(b);
if (a == b) return;
if (size[a] < size[b]) swap(a, b);
par[b] = a;
size[a] += size[b];
}
};
signed main()
{
fast();
#if _LOCAL
ifstream in("e://in.txt");
cin.rdbuf(in.rdbuf());
#endif
int n, w;
cin >> n >> w;
vvi b(n, vi(n, inf));
vvi c(n, vi(n, inf));
rep(i, n - 1)
{
rep(j, i + 1)
{
int cap;
cin >> cap;
c[i + 1][j] = cap;
c[j][i + 1] = cap;
}
}
rep(i, n - 1)
{
rep(j, i + 1)
{
int cap;
cin >> cap;
b[i + 1][j] = cap;
b[j][i + 1] = cap;
}
}
vector<tuple<int, int, int>> edges;
rep(i, n) rep(j, n)
{
if (i == j) continue;
if (w-c[i][j] <= b[i][j]) edges.emplace_back(i, j, c[i][j]);
}
sort(all(edges), [](tuple<int, int, int> a, tuple<int, int, int> b)
{
return get<2>(a) > get<2>(b);
});
vector<tuple<int, int, int>> mst;
UF uf(n);
for (auto [u, v, weight] : edges)
{
if (uf.find(u)!=uf.find(v))
{
uf.merge(u, v);
mst.emplace_back(u, v, w-weight);
}
}
edges = vector<tuple<int, int, int>>();
rep(i, n) rep(j, n)
{
if (i == j) continue;
if (w-c[i][j] <= b[i][j]) edges.emplace_back(i, j, b[i][j]);
}
sort(all(edges), [](tuple<int, int, int> a, tuple<int, int, int> b)
{
return get<2>(a) > get<2>(b);
});
uf = UF(n);
for (auto [u, v, weight] : edges)
{
if (uf.find(u) != uf.find(v))
{
uf.merge(u, v);
mst.emplace_back(u, v, weight);
}
}
auto wmat = [&](vector<vector<p2>>& adj)
{
vvi mat(n, vi(n, inf));
rep(i, n)
{
vi vis(n);
priority_queue<p2> pq;
pq.emplace(inf, i);
while (sz(pq))
{
int w, u;
tie(w, u) = pq.top();
pq.pop();
if (vis[u]) continue;
vis[u] = 1;
mat[i][u] = w;
repe(e, adj[u]) pq.emplace(min(w, e.second), e.first);
}
}
return mat;
};
auto testsol = [&](vector<tuple<int, int, int>> edges)
{
vector<vector<p2>> bikeadj(n), caradj(n);
for (auto [u, v, weight] : edges)
{
bikeadj[u].emplace_back(v, weight);
bikeadj[v].emplace_back(u, weight);
caradj[u].emplace_back(v, w - weight);
caradj[v].emplace_back(u, w - weight);
}
vvi dbike = wmat(bikeadj);
bool ret = dbike == b;
vvi cmat = wmat(caradj);
ret &= cmat == c;
return ret;
};
if (testsol(mst))
{
cout << sz(mst) << "\n";
for (auto [u, v, weight] : mst)
{
cout << u << " " << v << " " << weight << "\n";
}
}
else
{
cout << "NO";
}
return 0;
}
