#include<bits/stdc++.h> using namespace std; int prices[1010],n; int fg() { int res = 0; for(int i=0;i<n-1;++i) { int temp = prices[i+1] - prices[i]; if(temp>0) res += temp; } return res; } int main() { cin>>n; for(int i=0;i<n;i++) cin>>prices[i]; cout<<fg()<<endl; return 0; }