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