//CF448C
#include <cstdio>
int a[5005];

int main(){
	int n,sum=0;
	scanf("%d",&n);
	for(int i=1; i<=n; ++i)
		scanf("%d",&a[i]);
	for(int i=1; i<=n; ++i){
		if(a[i-1]<a[i] && a[i+1]<a[i])
			++sum,a[i]=a[i-1];
		if(a[i]>a[i-1])
			sum+=a[i]-a[i-1];
	}
	printf("%d",sum);
	return 0;
}