#include <bits/stdc++.h>
#define FI first
#define SE second
#define EPS 1e-9
#define ALL(a) a.begin(),a.end()
#define SZ(a) int((a).size())
#define MS(s, n) memset(s, n, sizeof(s))
#define FOR(i,a,b) for (int i = (a); i <= (b); i++)
#define FORE(i,a,b) for (int i = (a); i >= (b); i--)
#define FORALL(it, a) for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
//__builtin_ffs(x) return 1 + index of least significant 1-bit of x
//__builtin_clz(x) return number of leading zeros of x
//__builtin_ctz(x) return number of trailing zeros of x

using namespace std;
using ll = long long;
using ld = double;
typedef pair<int, int> II;
typedef pair<int, II> III;
typedef complex<ld> cd;
typedef vector<cd> vcd;

const ll MODBASE = 1000000007LL;
const int MAXN = 210;
const int MAXM = 100010;
const int MAXK = 110;
const int MAXQ = 200010;

int t[10], T, a[10];

bool check(int u) {
    FOR(i,1,4) a[i] = t[i];
    a[5] = u;
    sort(a+1, a+6);
    return a[2] + a[3] + a[4] <= 3 * T;
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(nullptr);
    ld x;
    FOR(i,1,4) {
        cin >> x;
        t[i] = int(x * 100);
    }
    cin >> x;
    T = int(x * 100);
    sort(t+1, t+4+1);
    if (t[2] + t[3] + t[4] <= 3 * T) cout << "infinite";
    else if (t[1] + t[2] + t[3] > 3 * T) cout << "impossible";
    else {
        int res = -1;
        FOR(i,0,2100)
            if (check(i)) res = i;
        cout << fixed << setprecision(2) << res / 100.0;
    }
    return 0;
}