import std.stdio, std.string, std.array, std.conv, std.algorithm;

void main() {
    int n = readln.chomp.to!int;
    double[] v = readln.split.to!(double[]);
    v.sort!("a > b");
    while (v.length > 1) {
        double tmp = v[$-1];
        v.popBack;
        v[$-1] = (v[$-1] + tmp) / 2.0;
    }
    writefln("%.8f", v[0]);
}