#include<algorithm>
using namespace std;
int n;
void solve(){
    int i,next,prev,k=0;
    scanf("%d%d",&n,&prev);
    for(i=1; i<n; ++i){
        scanf("%d",&next);
        if(next>prev)
            k+=next-prev;
        prev=next;}
    printf("%d",k);}
int main(){
    freopen("operatii.in","r",stdin);
    freopen("operatii.out","w",stdout);
    solve();
    return 0;}