#include <stdio.h>
long long v[1000000],n;

int main ()
 {
 long long i,x;
 FILE *f;
 f=fopen("operatii.in","r");
 fscanf(f,"%lld",&n);
 v[0]=0;
 x=0;
 for (i=1;i<=n;i++)
     {
     fscanf(f,"%lld",&v[i]);
     if (i>=2&&v[i]>v[i-1])
	x+=v[i]-v[i-1];
     }
 fclose(f);
 f=fopen("operatii.out","w");
 fprintf(f,"%lld",x);
 fclose(f);
 return 0;
 }