#include<stdio.h>

const char in[]="operatii.in";
const char out[]="operatii.out";

long long n, x, y, sol, i;

int main()
	{
		freopen(in,"r",stdin);
		freopen(out,"w",stdout);
		scanf("%lld", &n);
		for(i=1;i<=n;++i)
		{
			scanf("%lld", &x);
			if(x>y) sol+=x-y;
			y=x;
		}
		printf("%lld\n", sol);
		return 0;
}