#include <bits/stdc++.h>
typedef long long int ll;
#define endl            '\n'
#define pb             push_back
#define mp              make_pair
#define pll             pair<ll,ll> 
#define fill(x, y)     memset(x, y, sizeof(x))
#define all(x)         (x).begin(), (x).end()
#define debug(x)       { cerr << #x << " = " << x << endl; }
#define IO	       { ios_base::sync_with_stdio(false); cin.tie(0); }
#define read(x)	       freopen(x, "r", stdin)
#define write(x)       freopen(x, "w", stdout)
#define N       1000000

using namespace std;

typedef vector<int> vi;

int inp() {
    string s;
    cin >> s;
    int val = 0;
    for (char c: s) {
        if (c >= '0' and c <= '9') val = val * 10 + (c - '0');
    }
    return val;
}

int main(){
    IO;
    cout<<fixed<<setprecision(2);
    vector<int> t;
    for (int i=0; i<4; i++) {
        
        t.push_back(inp());
    }
    sort(all(t));
    int tt = inp();

    int valid = -1;
    for (int i=0; i<2002; i++) {
        vector<int> cpy(t);
        cpy.push_back(i);
        sort(all(cpy));

        int sum = cpy[1] + cpy[2] + cpy[3];
        if (sum <= 3*tt) valid = i;
    }

    if (valid == -1) {
        cout << "impossible" << endl;
    } else if (valid == 2001) {
        cout << "infinite" << endl;
    } else {
        int x = valid / 100;
        int y = valid % 100;
        int k1 = y/10;
        int k2 = y%10;
        cout << x << "." << k1 << k2 << endl;
    }
    
}