23 out of 5

#include<bits/stdc++.h>

using namespace std;

bool flag;

int arr[7];

void solve(int index,int val)
{
    if(index==5 && val==23)
    {
        flag = true;
        return;
    }

    if(index>=5)
        return;

    solve(index+1,val+arr[index]);

    solve(index+1,val-arr[index]);

    solve(index+1,val*arr[index]);
}

int main()
{
    int i;

    while(scanf("%d",&arr[0])&&arr[0])
    {
        for(i=1;i<5;i++)
        {
            scanf("%d",&arr[i]);
        }

        sort(arr,arr+5);

        flag = false;

        solve(1,arr[0]);

        while(!flag && next_permutation(arr,arr+5))
        {
            solve(1,arr[0]);
        }

        if(flag)
        {
            printf("Possible\n");
        }
        else
        {
            printf("Impossible\n");
        }
    }

    return 0;
}