https://codeforces.com/problemset/problem/1009/D
Ideas:
The special points are connected from 1 to every point, then 2, 3....
In fact, it is equivalent to each i and the primal connection with itself in the front. Then it is Euler's function. Each i is the prefix sum of Euler functions.
So violence is enough.
#include<iostream>
#include<vector>
#include<queue>
#include<cstring>
#include<cmath>
#include<map>
#include<set>
#include<cstdio>
#include<algorithm>
#define debug(a) cout<<#a<<"="<<a<<endl;
using namespace std;
const int maxn=1e5+100;
typedef long long LL;
inline LL read(){LL x=0,f=1;char ch=getchar(); while (!isdigit(ch)){if (ch=='-') f=-1;ch=getchar();}while (isdigit(ch)){x=x*10+ch-48;ch=getchar();}
return x*f;}
int main(void)
{
cin.tie(0);std::ios::sync_with_stdio(false);
LL n,m;cin>>n>>m;
LL sum=0;
vector<pair<LL,LL>>v;
bool flag=1;
for(LL i=1;flag==1&&i<=n;i++){
for(LL j=i+1;flag==1&&j<=n;j++){
if(__gcd(i,j)==1){
v.push_back({i,j});
sum++;
}
if(sum>=m){
flag=0;
break;
}
}
}
if(flag==1||sum<n-1){
cout<<"Impossible"<<"\n";
}
else{
cout<<"Possible"<<"\n";
for(auto i:v){
cout<<i.first<<" "<<i.second<<"\n";
}
}
return 0;
}