#include<stdio.h>   
int n,v[1000000];   
void citire()   
{   
    for(int i=1;i<=n;++i)   
        scanf("%d",&v[i]);   
}   
int main()   
{   
    long long nr=0,p=0;   
    freopen("operatii.in","r",stdin);   
    freopen("operatii.out","w",stdout);   
    scanf("%d",&n);   
    citire();   
    for(int i=1;i<=n;i++)   
    {   
        if(v[i]>v[p])   
            nr=nr-v[p]+v[i];  
        p=i;    
    }   
    printf("%lld",nr);   
    return 0;   
}