import std;

void main () {
    int N = readln.chomp.to!int;
    auto A = readln.split.to!(int[]);

    int[int] mp;
    foreach (v; A) mp[v]++;

    int ans = 0;
    foreach (key, val; mp) ans += val / 2;

    writeln(ans);
}

void read (T...) (string S, ref T args) {
    import std.conv : to;
    import std.array : split;
    auto buf = S.split;
    foreach (i, ref arg; args) {
        arg = buf[i].to!(typeof(arg));
    }
}