#include<stdio.h>      
long long n,nr,ua,a,i;      
int main()      
{      
 FILE *f=fopen("operatii.in","r"), *g=fopen("operatii.out","w");      
 
 fscanf(f,"%lld",&n);      
 nr=0;      
 ua=0;      
 for(i=1;i<=n;++i)      
    {fscanf(f,"%lld",&a);      
     if(a>ua)nr=nr+a-ua;      
     ua=a;}      
	
 fprintf(g,"%lld\n",nr);      
 fclose(f);
 fclose(g);
 return 0;      
}