#include<iostream>
using namespace std;
int v[32002],n,i,f[32002];
unsigned long long int k;
int main()
{
    cin>>n;
    for(i=1;i<=n;i++)
        cin>>v[i];
        v[n+1]=0;
    for(i=1;i<=n;i++)
    {
        if(v[i]<v[i+1])
            f[i]=0;
        else
            f[i]=f[i-1]+1;
        if((f[i]==0 && f[i-1]>1))
            k+=f[i-1]/2;
    }
    if(f[n]>1)
    cout<<k+f[n]/2;
    else
        cout<<k;
    return 0;
}