#include <stdio.h>

const int N_MAX = 1000010;

int v[N_MAX];

int main()
{
	freopen("operatii.in", "r", stdin);
#ifndef _SCREEN_
	freopen("operatii.out", "w", stdout);
#endif

	int N, i;
	scanf("%d\n", &N);
	for (i = 1; i <= N; i ++) {
		scanf("%d ", &v[i]);
	}

	int scad = 0, j;
	long long rez = 0;

	for (i = 1; i <= N;) {
		for (j = i + 1; v[j] >= v[j - 1] && j <= N; j ++);
		rez += (v[j - 1] - scad);

		for (; v[j] <= v[j - 1] && j <= N; j ++);
		scad = v[j - 1];
		i = j;
	}

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

	return 0;
}