#include <stdio.h>

#define MAXN 1000005

int N, x[MAXN];

int main()
{
	freopen("operatii.in", "rt", stdin);
	freopen("operatii.out", "wt", stdout);

	scanf("%d", &N);
	for (int i = 0; i < N; i++)
		scanf("%d", x + i);

	long long NR = x[0];
	for (int i = 1; i < N; i++)
	{
		if (x[i] < x[i - 1]) continue;
		NR += x[i] - x[i - 1];
	}

	printf("%lld\n", NR);

	return 0;
}