code forces 1173 B. Nauuo and Chess(构造)

//#include<bits/stdc++.h>
#include<iostream>
#include<cstdio>
#include<cstring>
#include<string>
#include<set>
#include<vector>
#include<map>
#include<stack>
#include<queue>
#include<cmath>
#include<fstream>
#include<algorithm>
using namespace std;

#define rep(i,a,n) for(int i=a;i<=n;i++)
#define per(i,a,n) for(int i=n;i>=a;i--)
//#define CLR(a) memset(a,sizeof(a),0)

typedef long long ll;
typedef unsigned long long ull;

const int INF = 0x3f3f3f3f;
const int maxn=1e6+10;


int main(){
    int n,m;
    scanf("%d", &n);
    rep(i,1,n){
        if(i*2-1>=n){
            m=i;
            break;
        }
    }
    printf("%d ", m);
    rep(i,1,m){
       rep(j,i,i+1){
            if(n>0){
                --n;
                printf("%d %d ",i,j);
            }else{
                break;
            }
       }
       if(n<=0)break;
    }
    return 0;
}