"use strict"
const create = () => {
    const input = require("fs").readFileSync("/dev/stdin", "utf8").trim().split("\n");
    const res = {
        "list": input, "index": 0, "max": input.length,
        "hasNext": function () { return this.index < this.max },
        "next": function () { if (!this.hasNext()) { throw "ArrayIndexOutOfBoundsException"; } else { return this.list[this.index++]; } }
    };
    return res;
}
const o = create();
const next = () => o.next()
const nextInt = () => parseInt(o.next())
const nextStrArray = () => o.next().split(" ")
const nextIntArray = () => o.next().split(" ").map(el => parseInt(el))
const nextCharArray = () => o.next().split("")
const hasNext = () => o.hasNext()
const myout = (...x) => console.log(...x)
const Main = () => {
    const N = nextInt()
    const a = nextIntArray()
    let m = {}
    for (let el of a) {
        if (!m[el]) m[el] = 1
        else m[el]++
    }
    let cnt = 0
    for (let key of Object.keys(m)) {
        if (m[key] < key) {
            cnt += m[key]
        } else if (m[key] > key) {
            cnt += m[key] - Number(key)
        }
    }
    console.log(cnt)
}
Main()
