#include <bits/stdc++.h>
using namespace std;
#define ll long long
const int N = 1e6 + 9;
const int mod = 1e9+7;
#define inf 8e10

int dep[N];
vector<int> g[N];
void solve()
{
    ll a,b;char c;cin>>a>>c>>b;
    if(a*1.0/b < 0.5) 
    {
        cout<<"impossible"<<'\n';
        return ;
    }

    ll x=a,y=b;
    while(1)
    {
        if(y * (y - 1) / 2 >= x && (y - 1) <= x) break;
        x += a,y += b;
    }

    int pos=2,sum=0;
    dep[1]=0;
    for(int i=2;i<=y;++i) dep[i]=1,sum+=1;

    if(sum>x)
    {
        cout<<"impossible"<<'\n';
        return ;
    }

    cout<< y <<' ' << y - 1<<'\n';

    while(1)
    {
        if(sum==x) break;
        int i;
        for(i=y;i>pos;--i) 
        {
            dep[i]++;
            if(++sum == x) break;
        }
        if(i==pos) pos++;
        if(sum==x) break;
    }

   // for(int i=1;i<=y;++i) cout<<dep[i]<<' ';
   int now=1;
   for(int i=2;i<=y;++i)
   {
        if(dep[i]==dep[now] + 1) g[now].push_back(i);
        else 
        {
            now = i - 1;
            i--;
        }
   }
   
   for(int i=1;i<=y;++i)
   {
        for(auto &y:g[i])
            cout<<i<<' '<<y<<'\n';
   }
}
int main()
{
    ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
    int _ = 1; // cin>>_;
    while (_--) solve();
    return 0;
}