#include<stdio.h>

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