#include<bits/stdc++.h>
using namespace std;
#define int long long
#define fall(i,a,b) for(int i=a;i<=b;i++)
#define rfall(i,a,b) for(int i=a;i>=b;i--)
#define pb push_back
#define F first
#define all(x) x.begin(),x.end()
#define S second
#define sz(x) (int)x.size()
const int MAXN=5e2+10;
typedef pair<int,int> pii;
typedef tuple<int,int,int> trio;
int c[MAXN][MAXN],n,b[MAXN][MAXN],W,B,pai[MAXN];
vector<trio> roads;
vector<pii> g[MAXN];
bool ok=1;
void show(vector<trio> arr){
cout<<sz(arr)<<"\n";
for(auto [u,j,k]:arr) cout<<u<<" "<<j<<" "<<k<<"\n";
}
int find(int x){
return x==pai[x]?x:pai[x]=find(pai[x]);
}
void merge(int a,int b){
a=find(a),b=find(b);
pai[a]=b;
}
void dfs(int x,int ini,int p,int val){
ok&=(val==c[x][ini]);
for(auto [u,w]:g[x]){
if(u==p) continue;
dfs(u,ini,x,max(val,w));
}
}
void build_KRT(){
vector<trio> ord;
fall(i,0,n-1)
fall(j,i+1,n-1) ord.pb({c[i][j],i,j});
fall(i,0,n-1) pai[i]=i;
sort(all(ord),greater<>());
for(auto [w,a,b]:ord){
if(find(a)==find(b)) continue;
merge(a,b);
g[a].pb({b,w}); g[b].pb({a,w});
roads.pb({a,b,W-w});
}
fall(i,0,n-1) dfs(i,i,-1,0);
}
int32_t main(){
std::ios_base::sync_with_stdio(false);
cin.tie(NULL);
cin>>n>>W;
fall(i,1,n-1)
fall(j,0,i-1) cin>>c[j][i],c[i][j]=c[j][i];
fall(i,1,n-1)
fall(j,0,i-1) cin>>b[j][i],b[i][j]=b[j][i];
B=b[0][1];
fall(i,1,n-1)
fall(j,0,i-1){
if(c[i][j]+B<W){
cout<<"NO\n";
return 0;
}
}
fall(i,0,n-2) roads.pb({i,i+1,B});
build_KRT();
if(!ok){
cout<<"NO\n";
return 0;
}
show(roads);
}
