#include<stdio.h>
#define lg 1000001
int a[lg],n,max,nr,i;
int main()
{freopen("operatii.in","r",stdin);
 freopen("operatii.out","w",stdout);
 scanf("%d",&n);
 for(i=0;i<n;i++) 
 {scanf("%d",&a[i]);
  if(a[i]>max) max=a[i];}
 for(;max;max--){
	 i=0;
	 while(i<n){
		 while(!a[i]&&i<n)i++;
		 if(i==n) break;
		 nr++;
		 while(a[i]&&i<n) i++,a[i]--;}
 }
 printf("%d",nr);
 fclose(stdout);
 return 0;}