# include <stdio.h>

# define input "operatii.in"
# define output "operatii.out"

# define max 1000001
# define maxim(a,b) (a>b?a:b)

int a[max];
int i,n;
int res;

int main()
{
    freopen( input, "r", stdin );
    freopen( output, "w", stdout );
    
    scanf("%d", &n);
    scanf("%d", &a[0]);
    
    for(i=1;i<n;i++)
    {
       scanf("%d",&a[i]);
       if(a[i] > a[i-1])
          res+=a[i]-a[i-1];
    }

    
    printf("%d",res);
    
    return 0;
}