import std.stdio, std.string, std.conv, std.algorithm, std.numeric;
import std.range, std.array, std.math, std.typecons, std.container, core.bitop;


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

    auto cnt = new int[](10^^5 + 10);
    int over;

    foreach (ai ; a) {
        if (ai > 10^^5) {
            over++;
        }
        else {
            cnt[ai]++;
        }
    }

    debug {
        writeln(cnt[0 .. 20]);
    }

    int ans = over;

    foreach (i ; 0 .. 10^^5 + 1) {
        int d = cnt[i];

        if (cnt[i] >= i && d > cnt[i] - i) {
            d = cnt[i] - i;
        }
        
        ans += d;
    }

    writeln(ans);
}



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



void fillAll(R, T)(ref R arr, T value) {
    static if (is(typeof(arr[] = value))) {
        arr[] = value;
    }
    else {
        foreach (ref e; arr) {
            fillAll(e, value);
        }
    }
}