#include<bits/stdc++.h>
#define rep(i,j,k) for(int i=j;i<=k;i++)
#define repp(i,j,k) for(int i=j;i>=k;i--)
#define ls(x) (x<<1)
#define rs(x) ((x<<1)|1)
#define mp make_pair
#define sec second
#define fir first
#define pii pair<int,int>
#define lowbit(i) i&-i
#define int long long
#define double long double
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
const int N=505,M=5e5+5,S=(1<<15)+5,inf=(ll)1e18+7,mo=1e9+7;
const double eps=1e-8;
void read(int &p){
	int x=0,w=1;
	char ch=0;
	while(!isdigit(ch)){
		if(ch=='-')w=-1;
		ch=getchar();
	}
	while(isdigit(ch)){
		x=(x<<1)+(x<<3)+ch-'0';
		ch=getchar();
	}
	p=x*w;
}
int n,w,b[N][N],c[N][N],cntb,cntc;
struct edge{
    int x,y,v;
    friend bool operator<(edge x,edge y){
        return x.v>y.v;
    }
}eb[N*N],ec[N*N];
vector<edge>ans;
int valb[N][N],valc[N][N];
struct bcj{
    int fa[N];
    void init(){
        rep(i,1,n)
            fa[i]=i;
    }
    int find(int x){
        if(fa[x]==x)return x;
        return fa[x]=find(fa[x]);
    }
    bool merge(int x,int y){
        x=find(x),y=find(y);
        if(x==y)return 0;
        fa[x]=y;
        return 1;
    }
}B;
signed main(){
    read(n),read(w);
    rep(j,2,n){
        rep(i,1,j-1)
            read(c[i][j]),ec[++cntc]=(edge){i,j,c[i][j]};
    }
    rep(j,2,n){
        rep(i,1,j-1)
            read(b[i][j]),eb[++cntb]=(edge){i,j,b[i][j]};
    }
    sort(eb+1,eb+cntb+1),sort(ec+1,ec+cntc+1);
    rep(i,1,n){
        rep(j,1,n)
            valb[i][j]=valc[i][j]=(i==j?0:-inf);
    }
    B.init();
    rep(i,1,cntb){
        int x=eb[i].x,y=eb[i].y,v=eb[i].v;
        if(c[x][y]+v<w)continue;
        if(B.merge(x,y))ans.push_back((edge){x,y,v}),valb[x][y]=valb[y][x]=v;
    }
    B.init();
    rep(i,1,cntc){
        int x=ec[i].x,y=ec[i].y,v=ec[i].v;
        if(b[x][y]+v<w)continue;
        if(B.merge(x,y))ans.push_back((edge){x,y,w-v}),valc[x][y]=valc[y][x]=v;
    }
    rep(k,1,n){
        rep(i,1,n){
            rep(j,1,n){
                valb[i][j]=max(valb[i][j],min(valb[i][k],valb[k][j]));
                valc[i][j]=max(valc[i][j],min(valc[i][k],valc[k][j]));
            }
        }
    }
    bool ok=1;
    rep(i,1,n){
        rep(j,i+1,n)
            if(valb[i][j]!=b[i][j]||valc[i][j]!=c[i][j])ok=0;
    }
    if(!ok)puts("NO");
    else{
        printf("%lld\n",ans.size());
        for(auto j:ans)
            printf("%lld %lld %lld\n",j.x-1,j.y-1,j.v);
    }
    return 0;
}