#include<stdio.h>
#include<string.h>
long a,b,c,d,e,f,mem,n,i,j;
int s[1111];
FILE *f1,*f2;
void adunare(){
int i;
i=0;
mem=0;
while(c||mem){
	i++;
	d=s[i]+c%10+mem;
	s[i]=d%10;
	mem=d/10;
	c=c/10;
}
if(i>j){j=i;}
}
int main(){
f1=fopen("operatii.in","r");
f2=fopen("operatii.out","w");
fscanf(f1,"%ld%ld",&n,&b);
c=b;
while(c!=0){
	j++;
	s[j]=c%10;
	c=c/10;
}
j=0;
for(i=2;i<=n;i++){
	a=b;
	fscanf(f1,"%ld",&b);
	c=b-a;
	if(c>0){adunare();}
}
for(i=j;i>=1;fprintf(f2,"%d",s[i]),i--);
return 0;}