Submission #70011223

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Source Code Expand

#include <bits/stdc++.h>
using namespace std;
#define rep(i,a,n) for (int i=(a);i<(n);i++)
#define per(i,a,n) for (int i=(n)-1;i>=(a);i--)
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define all(x) (x).begin(),(x).end()
#define fi first
#define se second
#define SZ(x) ((int)(x).size())
typedef vector<int> VI;
typedef basic_string<int> BI;
typedef long long ll;
typedef pair<int,int> PII;
typedef double db;
mt19937 mrand(random_device{}()); 
const ll mod=1000000007;
int rnd(int x) { return mrand() % x;}
ll powmod(ll a,ll b) {ll res=1;a%=mod; assert(b>=0); for(;b;b>>=1){if(b&1)res=res*a%mod;a=a*a%mod;}return res;}
ll gcd(ll a,ll b) { return b?gcd(b,a%b):a;}
// head

int n;
vector<PII> eg;
int main() {
	scanf("%d",&n);
	if (n<=5) {
		puts("-1");
		return 0;
	}
	if (n%2==0) {
		rep(i,1,n/2+1) {
			rep(j,n/2+1,n+1) {
				if (i+j!=n+1) {
					eg.pb(mp(i,j));
				}
			}
		}
	} else {
		rep(i,1,n/2+1) {
			rep(j,n/2+1,n+1) {
				if (i+j!=n) {
					eg.pb(mp(i,j));
				}
			}
		}

	}
	printf("%d\n",SZ(eg));
	for (auto [x,y]:eg) printf("%d %d\n",x,y);
}

Submission Info

Compile Error

Main.cpp: In function ‘int main()’:
Main.cpp:27:14: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
   27 |         scanf("%d",&n);
      |         ~~~~~^~~~~~~~~

Judge Result