#include <bits/stdc++.h>

using namespace std;

typedef long long ll;

int n;
ll x, prevx, ans;

inline ll vabs(const ll X) { return (X > 0 ? X : -X); }

int main()
{
    freopen("operatii.in", "r", stdin);
    freopen("operatii.out", "w", stdout);
    scanf("%d", &n);
    while(n--)
        scanf("%lld", &x),
        ans += vabs(prevx - x),
        prevx = x;
    ans += x, printf("%lld", ans / 2);
    return 0;
}