//#pragma GCC target("avx2")
//#pragma GCC optimize("O3")
//# include <x86intrin.h>
# include <bits/stdc++.h>
//# include <ext/pb_ds/assoc_container.hpp>
//# include <ext/pb_ds/tree_policy.hpp>
//using namespace __gnu_pbds;
using namespace std;
//template<typename T> using ordered_set = tree <T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define _USE_MATH_DEFINES_
#define ll long long
#define ld long double
#define Accepted 0
#define pb push_back
#define mp make_pair
#define sz(x) (int)(x.size())
#define every(x) x.begin(),x.end()
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define For(i,x,y) for (ll i = x; i <= y; i ++)
#define FOr(i,x,y) for (ll i = x; i >= y; i --)
#define SpeedForce ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0)
// ROAD to... Red
inline void Input_Output () {
//freopen(".in", "r", stdin);
//freopen(".out", "w", stdout);
}
const double eps = 0.000001;
const ld pi = acos(-1);
const int maxn = 1e7 + 9;
const int mod = 1e9 + 7;
const ll MOD = 1e18 + 9;
const ll INF = 1e18 + 123;
const int inf = 2e9 + 11;
const int mxn = 1e6 + 9;
const int N = 6e5 + 123;
const int M = 22;
const int pri = 997;
const int Magic = 2101;
const int dx[] = {-1, 0, 1, 0};
const int dy[] = {0, -1, 0, 1};
int n, m, k;
vector < pair < int, int > > e;
int lst, ptr;
int main () {
scanf("%d", &k);
e.pb({0, -1});
int cur = 1;
while(k >= cur) {
k-=cur;
e.pb({++ptr, lst});
lst = ptr;
++cur;
}
if (k) {
e.pb({++ptr, k-1});
}
printf("%d\n", sz(e));
for (auto it : e) {
printf("%d %d\n", it.first, it.second);
}
return Accepted;
}
// B...a
