#include <stdio.h>
#define N 1000012
int v[N];
int main()
{
	int n,i,nr,oper=0,m=0;
	freopen("operatii.in", "r",stdin);
	freopen("operatii.out", "w",stdout);
	scanf("%d", &n);
	for(i=1;i<=n;++i)
		scanf("%d", &v[i]); 
	for(m=1;m<=100000;++m)
		{nr=0;
			for(i=0;i<=n+1;++i)
			{	
				if(v[i]<m && v[i+1]>=m) 
					{++oper; ++nr;}	
		   	}
			if(nr==0) break;
		}	
	printf("%d\n", oper);
	return 0;
}