#include <stdio.h>
int nr,n;
long long counter;
int main()
{
    freopen ("operatii.in","r",stdin);
    freopen ("operatii.out","w",stdout);
    scanf("%d",&n);
    int nrtemp;
    scanf("%d",&nrtemp);
    for(int i=2;i<=n;i++)
    {
            scanf("%d",&nr);
            if(nr>nrtemp) counter+=nr-nrtemp;
            nrtemp=nr;
    }
    printf("%lld\n",counter);
}