#include <cstdio>

using namespace std;

int main()
{   freopen("operatii.in", "r",stdin);
    freopen("operatii.out", "w",stdout);
    int n,i,a,b;
    long long op=0;
    scanf("%d", &n);
    scanf("%d", &a);
    for(i=2; i<=n; i++){
      scanf("%d", &b);
      if(b-a>0)
        op=op+b-a;
      a=b;
    }
    printf("%d", op);
    return 0;
}