Goodbye Wuxu 题解

#include<bits/stdc++.h>
#define LL long long
#define rep(i,s,t) for(register int i = (s),i##end = (t); i <= i##end; ++i)
#define dwn(i,s,t) for(register int i = (s),i##end = (t); i >= i##end; --i)
using namespace std;
inline int read()
{
    int x=0,f=1;char ch;
    for(ch=getchar();!isdigit(ch);ch=getchar())if(ch==‘-‘)f=-f;
    for(;isdigit(ch);ch=getchar())x=10*x+ch-‘0‘;
    return x*f;
}
int n,m;
void pute(int x, int y){cout << x << " " << y << " ";}
int main()
{
    m = n = read();if(n & 1)m--;
    cout << (n / 2) << endl;
    rep(i, 1, n/2)
    {
        int x = i, y = i + 1;
        pute(x, y);
        rep(j, 1, m/2-1)
        {
            x--;if(x == 0)x = m;
            pute(x, y);
            y++;if(y == m+1)y = 1;
            pute(x, y);
        }
        if(n & 1)pute(i, n);
        cout << endl;
    }
}