#include<bits/stdc++.h>
using namespace std;
int n,k,b,a[10010],s[10010],t,ans;
int main()
{
cin>>n>>k>>b;
for(int i=1;i<=b;++i)
{
cin>>t;
a[t]=1;
}

for(int i=1;i<=n;++i)
s[i]=s[i-1]+a[i];

ans=n;

for(int i=1;i<=n-k+1;++i)
ans=min(ans,s[i+k-1]-s[i-1]);

cout<<ans;
return 0;
 }