package olymp;

import net.egork.io.IOUtils;
import net.egork.misc.ArrayUtils;
import net.egork.utils.io.InputReader;
import net.egork.utils.io.OutputWriter;

public class RCC_C {
    public void solve(int testNumber, InputReader in, OutputWriter out) {
        int n = in.readInt();
        int[] a = IOUtils.readIntArray(in, n);
        if (n == 1) {
            out.printLine(a[0]);
            return;
        }
        int max = ArrayUtils.maxElement(a);
        int pos = 0;
        int sum = 0;
        double best = max / 2.0;
        while (sum <= max) {
            if (sum <= best) {
                int rem = a[pos] - sum;
                best = Math.max(best, Math.max(sum, rem));
            } else {
                best = Math.max(best, a[pos] / 2.0);
            }
            sum += a[pos];
            pos++;
        }
        out.printLine(best);
    }
}