#include<stdio.h>
long long sum;
int main(){
	freopen("operatii.in","r",stdin);
	freopen("operatii.out","w",stdout);
	long long n,i,a,b;
	scanf("%lld",&n);
	scanf("%lld",&a);
	sum=a;
	for(i=1;i<n;++i){
		scanf("%lld",&b);
		if(b>a)
			sum+=b-a;
		a=b;
	}
	
	printf("%lld\n",sum);
	fclose(stdin);
	fclose(stdout);
	return 0;
}