#include <cstdio>
#include <cstdlib>
using namespace std;

int N, last, now, i;
long long ans;

int main()
{
    freopen("operatii.in", "r", stdin);
    freopen("operatii.out", "w", stdout);
    for(scanf("%i", &N), i = 1; i <= N; i++, last = now)
    {
        scanf("%i", &now);
        if(now > last) ans += 1LL * (now - last);
    }
    printf("%lld\n", ans);
    return 0;
}