//https://atcoder.jp/contests/abc146/tasks/abc146_e

#include <bits/stdc++.h>
using namespace std;
 
typedef long long ll;
typedef long double ld; 
typedef double db; 
typedef string str; 

typedef pair<int, int> pi;
typedef pair<ll,ll> pl; 
typedef pair<ld,ld> pd; 

typedef vector<int> vi; 
typedef vector<ll> vl;
typedef vector<ld> vd; 
typedef vector<str> vs; 
typedef vector<pi> vpi;
typedef vector<pl> vpl; 

#define FOR(i,a,b) for (int i = (a); i < (b); ++i)
#define F0R(i,a) FOR(i,0,a)
#define ROF(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define R0F(i,a) ROF(i,0,a)
#define trav(a,x) for (auto& a: x)

#define sz(x) (int)x.size()
#define all(x) begin(x), end(x)
#define rall(x) rbegin(x), rend(x) 
#define rsz resize
#define ins insert 

#define mp make_pair
#define pb push_back
#define eb emplace_back 
#define f first
#define s second
#define lb lower_bound 
#define ub upper_bound 

const int MOD = 1e9+7; // 998244353; // = (119<<23)+1
const int MX = 2e5+5;
const ll INF = 1e18; 
const ld PI = 4*atan((ld)1); 

namespace input {
	template<class T> void re(complex<T>& x);
	template<class T1, class T2> void re(pair<T1,T2>& p);
	template<class T> void re(vector<T>& a);
	template<class T, size_t SZ> void re(array<T,SZ>& a);

	template<class T> void re(T& x) { cin >> x; }
	void re(double& x) { string t; re(t); x = stod(t); }
	void re(ld& x) { string t; re(t); x = stold(t); }
	template<class T, class... Ts> void re(T& t, Ts&... ts) { 
		re(t); re(ts...); 
	}

	template<class T> void re(complex<T>& x) { T a,b; re(a,b); x = cd(a,b); }
	template<class T1, class T2> void re(pair<T1,T2>& p) { re(p.f,p.s); }
	template<class T> void re(vector<T>& a) { F0R(i,sz(a)) re(a[i]); }
	template<class T, size_t SZ> void re(array<T,SZ>& a) { F0R(i,SZ) re(a[i]); }
}

using namespace input;

namespace output {
	void pr(int x) { cout << x; }
	void pr(long x) { cout << x; }
	void pr(ll x) { cout << x; }
	void pr(unsigned x) { cout << x; }
	void pr(unsigned long x) { cout << x; }
	void pr(unsigned long long x) { cout << x; }
	void pr(float x) { cout << x; }
	void pr(double x) { cout << x; }
	void pr(ld x) { cout << x; }
	void pr(char x) { cout << x; }
	void pr(const char* x) { cout << x; }
	void pr(const string& x) { cout << x; }
	void pr(bool x) { pr(x ? "true" : "false"); }
	template<class T> void pr(const complex<T>& x) { cout << x; }
	
	template<class T1, class T2> void pr(const pair<T1,T2>& x);
	template<class T> void pr(const T& x);
	
	template<class T, class... Ts> void pr(const T& t, const Ts&... ts) { 
		pr(t); pr(ts...); 
	}
	template<class T1, class T2> void pr(const pair<T1,T2>& x) { 
		pr("{",x.f,", ",x.s,"}"); 
	}
	template<class T> void pr(const T& x) { 
		pr("{"); // const iterator needed for vector<bool>
		bool fst = 1; for (const auto& a: x) pr(!fst?", ":"",a), fst = 0; 
		pr("}");
	}
	
	void ps() { pr("\n"); } // print w/ spaces
	template<class T, class... Ts> void ps(const T& t, const Ts&... ts) { 
		pr(t); if (sizeof...(ts)) pr(" "); ps(ts...); 
	}
	
	void pc() { pr("]\n"); } // debug w/ commas
	template<class T, class... Ts> void pc(const T& t, const Ts&... ts) { 
		pr(t); if (sizeof...(ts)) pr(", "); pc(ts...); 
	}
	#define dbg(x...) pr("[",#x,"] = ["), pc(x);
}

using namespace output;

int main() {
	cin.sync_with_stdio(0); cin.tie(0); 
	// you should actually read the stuff at the bottom
	//freopen("a.in", "r", stdin);
	ll n, k; re(n, k);
	vl v(n); re(v);
	map<ll, ll> mmm;
	mmm[0]++;
	vl pre(n+1);
	ll ans = 0;
	pre[0] = 0;
	FOR(i, 1, n+1) pre[i] = ((pre[i-1]+v[i-1]-1)%k+k)%k;
	//ps(pre);
	if(k == 1){
		ps(0); return 0;
	}
	FOR(i, 1, n+1){
		ans += mmm[pre[i]];
		//ps(i, pre[i], mmm[pre[i]]);
		if(i >= k-1) {
			mmm[pre[i-k+1]]--;
			//ps(i, mmm[pre[i-k+1]]);
		} // 0 3 0 3 0 3 0 3 0
		mmm[pre[i]]++;
	}
	ps(ans);
}

/* stuff you should look for
	* int overflow, array bounds
	* special cases (n=1?), slow multiset operations
	* do smth instead of nothing and stay organized
*/

Measured memory_bytes: 15872