#include<iostream>
#include<string>

using namespace std;

int main()
{
    int N,nr;
    
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
    
    scanf("%d",&N);
    
    int last=0;
    long long ans=0;
    
    for(int i=1;i<=N;++i)
    {
       scanf("%d",&nr);
       if(nr<last) ans+=last-nr;
       last=nr;
    }   
    
    nr=0;
    if(nr<last) ans+=last-nr;
    
    printf("%lld",ans);
    
    return 0;
}