import std.stdio, std.math, std.algorithm, std.array, std.string, std.conv, std.container, std.range;
pragma(inline, true) T[] Reads(T)() { return readln.split.to!(T[]); }
alias reads = Reads!int;
pragma(inline, true) void scan(Args...)(ref Args args) {
    string[] ss = readln.split;
    foreach (i, ref arg ; args) arg = ss[i].parse!int;
}

void main() {
    int n; scan(n);
    int[] v = reads();
    v.sort();
    double x = v[0];
    foreach (i; v[1..$])
        x = (x + i) / 2.0;
    writefln("%.10f", x);
}
