#include<iostream>
using namespace std;
const int N=1e5+10;
int val[N];
int main()
{
int n;
cin>>n;
for(int i=0;i<n;i++)
cin>>val[i];
int res=0;
for(int i=0;i<n-1;i++)
{
if(val[i+1]>val[i])
res+=val[i+1]-val[i];
}
cout<<res<<endl;
return 0;
}