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*** The hack uses generator ***
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** Command line arguments **
no arguments

** Generated test **
200000
1 2
2 3
3 4
4 5
5 6
6 7
7 8
8 9
9 10
10 11
11 12
12 13
13 14
14 15
15 16
16 17
17 18
18 19
19 20
20 1
21 2
22 3
23 4
24 5
25 6
26 7
27 8
28 9
29 10
30 11
31 12
32 13
33 14
34 15
35 16
36 17
37 18
38 19
39 20
40 1
41 2
42 3
43 4
44 5
45 6
46 7
47 8
48 9
49 10
50 11
51 12
52 13
53 14
54 15
55 16
56 17
57 18
58 19
59 20
60 1
61 2
62 3
63 4
64 5
65 6
66 7
67 8
68 9
69 10
70 11
71 12
72 13
73 14
74 15
75 16
76 17
77 18
78 19
7...

** Generator source **
#ifdef LOCAL
//#define _GLIBCXX_DEBUG
#endif
//#pragma GCC target("avx512f,avx512dq,avx512cd,avx512bw,avx512vl")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

#define endl '\n'
#define REP(i, a, b) for(ll i=(a); i<(b); i++)
#define PER(i, a, b) for(ll i=(a); i>=(b); i--)
#define rep(i, n) REP(i, 0, n)

int solve(){
    ll n = 2e5;
    cout<<n<<endl;
    auto rand = [](ll n)->ll{
        random_device rd;
        mt19937 mt(rd());
        return mt()%n;
    };
    rep(i,n){
        cout<<(i+1)<<" "<<(i+1)%20+1<<endl;
    }
    return  0;
}

int main() {
    cin.tie(nullptr);
    ios::sync_with_stdio(false);
    cout<<std::setprecision(10);
    solve();
}