#include<stdio.h>
#define LMAX 1000000

long n,v[LMAX+1],sol,i,j;

int algoritm()
{int ad=1;
while(ad==1)
{ad=0;
 for(i=1;i<=n;i++)
 if(v[i]>0)
 {j=i; sol++; ad=1;
 while(v[j]>0) v[j++]--;
 i=j+1;}
}}


main()
{freopen("operatii.in","r",stdin);
 freopen("operatii.out","w",stdout);

 scanf("%ld",&n);

 for(i=1;i<=n;i++) scanf("%ld",&v[i]);

 algoritm();

 printf("%ld\n",sol);}