#include<cstdio>
using namespace std;
int nr1,i,n,nr,a[1000002];
int main()
{
freopen("operatii.in","r",stdin);
freopen("operatii.out","w",stdout);
scanf("%d",&n);
for(i=1;i<=n;i++)
	scanf("%d",&a[i]);
while(1)
{
	nr1=nr;
	for(i=1;i<=n;i++)
		if(a[i]!=0)
		{
			nr++;
			while(a[i]!=0)
			{
				a[i]--;
				i++;
			}
		}
	if(nr==nr1) break;
}
printf("%d\n",nr);
return 0;
}