205B - Little Elephant and Sorting - CodeForces Solution

#include<bits/stdc++.h>
using namespace std;
using ll = long long;

//Vishal Kumar Singh
//AVS
int main(){
   ll n,sum=0;
   cin>>n;
  ll a[n];
   for (int i = 0; i < n; i++)
   {
    cin>>a[i];
   }
     for (int i = 1; i < n; i++)
   {
     if (a[i-1]>a[i])
     {
        sum+=(a[i-1]-a[i]);
     }
     
   }
   cout<<sum;
    

   
}