#include <iostream>

using namespace std;

int a[1000005], n;

int main()
{
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
    
    int i, x;
    long long cont=0;
    
    scanf("%d",&n);
    
    for(i=1;i<=n;++i)
          scanf("%d",&a[i]);
    
    a[n+1]=0;
    a[0]=0;
    
    for(i=1;i<=n+1;++i)
           if(a[i]<a[i-1])
                   cont=cont+(a[i-1]-a[i]);
                   
    printf("%lld",cont);
    
    return 0;
}