import std.stdio, std.string, std.conv, std.algorithm;
import std.range, std.array, std.math, std.typecons;

int n;
int[] a;

void main() {
    scan(n);
    a = readln.split.to!(int[]);

    if (n & 1) {
        writeln(a[n/2]);
    }
    else {
        double ans = (a[n/2] + a[n/2 - 1]) / 2.0;
        writefln("%.1f", ans);
    }
}


void scan(T...)(ref T args) {
    auto line = readln.split;
    foreach (ref arg ; args) {
        arg = line.front.to!(typeof(arg));
        line.popFront();
    }
    assert(line.empty);
}