"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()
    let h = nextIntArray()
    h.push(-1)

    let sum = 0
    let arr = []
    let dir = true // up:true, down:false
    for(let i = 0; i<h.length-1;i++){
        if(dir && h[i] > h[i+1]){
            arr.push(h[i])
            dir = !dir
        }else if(!dir && h[i] < h[i+1]){
            arr.push(h[i])
            dir = !dir
        }
    }
    sum += arr[0]
    for(let i = 2; i<arr.length;i+=2){
        sum += arr[i]-arr[i-1]
    }
    console.log(sum)
}
Main()
