#include<bits/stdc++.h>
using namespace std;
namespace my_std{
#define mems(x,y) memset(x,y,sizeof x)
#define Mp make_pair
#define eb emplace_back
#define gc getchar
#define pc putchar
#define fi first
#define se second
#define il inline
#define rep(i,a,b) for(int i=(a);i<=(b);i++)
#define drep(i,a,b) for(int i=(a);i>=(b);i--)
#define go(i,u) for(int i=head[u];i;i=e[i].nxt)
	typedef long long ll;
	typedef pair<int,int> pii;
	template<typename T>
	il void read(T &x){
		int f=1;x=0;char c=gc();
		while(c<'0'||c>'9'){
			if(c=='-'){
				f=-1;
			}
			c=gc();
		}
		while(c>='0'&&c<='9'){
			x=x*10+c-48,c=gc();
		}
		x*=f;
	}
	template<typename T,typename ...Args>
	void read(T &x,Args &...args){
		read(x),read(args...);
	}
	template<typename T>
	il void write(T x){
		char buf[43];int len=0;
		if(x<0){
			pc('-'),x=-x;
		}
		do{
			buf[++len]=x%10,x/=10;
		}while(x);
		while(len){
			pc(buf[len--]+'0');
		}
	}
}
using namespace my_std;
const int N=5e4+7,M=-1,inf=0x3f3f3f3f,mod=0;
#define L(i) (((i)-1)*m+1)
#define R(i) min((i)*m,n)
int n,m,a[N],p[N],id[N];
bitset<N> f[N],pre[N],suf[N];
void Yorushika(){
	read(n,m);
	rep(i,1,n){
		read(a[i]);
		a[i]=n-a[i]+1;
		p[a[i]]=i;
	}
	bitset<N> t;
	rep(i,1,n){
		f[i]=t>>p[i];
		t.set(p[i]-1);
	}
	rep(i,1,n){
		id[i]=(i-1)/m+1;
	}
	rep(i,1,id[n]){
		pre[L(i)]=f[L(i)];
		rep(j,L(i)+1,R(i)){
			pre[j]=pre[j-1]&f[j];
		}
		suf[R(i)]=f[R(i)];
		drep(j,R(i)-1,L(i)){
			suf[j]=suf[j+1]&f[j];
		}
	}
	int ans=0;
	rep(i,1,n-m+1){
		bitset<N> r;
		if(i==L(id[i])){
			r=pre[R(id[i])];
		}else{
			r=suf[i]&pre[i+m-1];
		}
		ans+=r.count();
	}
	printf("%d\n",ans);
}
signed main(){
	int t=1;
	//read(t);
	while(t--){
		Yorushika();
	}
}