#include <iostream>
#include <vector>
#include <queue>
#include <set>

using namespace std;

int main() {
    int numOfTerr = 0;

    cin >> numOfTerr;

    vector<int> m_Heights;
    vector<int> open(1000000, -1);

    int curr = 0;
    int edges=0;
    for ( int i = 0; i < numOfTerr; i++ ) {
        cin >> curr;
        m_Heights.emplace_back(curr);
    }
    long long last=-1;
    for(int i = 0; i < m_Heights.size(); i++ ){
        if(open[m_Heights[i]]!=-1  && m_Heights[i]!=last ){
            edges+=i-open[m_Heights[i]]-1;
            open[m_Heights[i]]= i;
        }
        else{
            open[m_Heights[i]]= i;
        }
        for(int j=0;j< m_Heights[i];j++){
            open[j]= -1;
        }
        last=m_Heights[i];
    }

    cout << edges;
    return 0;
}