#include <bits/stdc++.h>
using namespace std;
const int N = 505;
struct node{
    int a,b,w;
    bool operator<(const node&x)const{
        return w<x.w;
    }
};
set<node> v;
int n,m,x,c,b;
int main() {
    // try the largest next edge, but before that check if theres already a larger connection
    cin>>n>>m;

    for(int i = 1;i<n;i++) {
        for(int j = 0;j<i;j++) {
            cin>>x;
            c = x;
            v.insert({i,j,m-x});
        }
    }
    for(int i = 1;i<n;i++) {
        for(int j = 0;j<i;j++) {
            cin>>x;
            b = x;
            v.insert({i,j,x});
        }
    }
    if(m-c > b || m - b > c) {
        cout << "NO\n";
        return 0;
    } 
    cout << v.size() << "\n";
    for(auto [a,b,c] : v)cout<<a<<" " << b << " " << c << "\n";

}

/*
2 1
0
1
*/