#include<stdio.h>
#include<string.h>
#define NM 1000001
int v[NM+1];
char s[NM*6+1];

int main(){
freopen("operatii.in","r",stdin);
freopen("operatii.out","w",stdout);
int n,i,j,nr=0,x,l;
char *p;
scanf("%d\n",&n);
fgets(s,NM*6+1,stdin);
l=strlen(s);
if(s[l-1]=='\n') s[l-1]=32,s[l]=0;
else s[l]=32,s[l+1]=0;
p=s;i=0;
while(*p){
	x=0;
	while(*p&&*p!=32) x=x*10+(*p-48),p++;
	v[++i]=x;
	if(*p&&*p==32)p++;
	}
for(i=1;i<=n;++i)
	if(v[i]>v[i-1]) nr+=v[i]-v[i-1];
printf("%d",nr);
return 0;
}