#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <fstream>
#include <queue>
#include <deque>
#include <bitset>
#include <iterator>
#include <list>
#include <stack>
#include <map>
#include <set>
#include <functional>
#include <utility>
#include <climits>
#include <cmath>
#include <cstdio>
#include <cstring>
#include <iomanip>
#include <cassert>
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 fast_cin() ios_base::sync_with_stdio(false); cin.tie(NULL)
 
#define forn(i,a,b) for (int i = (a); i < ll(b); ++i)
#define fo(i,a) forn(i,0,ll(a))
#define rforn(i,a,b) for (int i = (b)-1; i >= (a); --i)
#define ro(i,a) rforn(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
ll mod = 1000000000000000000;
inline int fast_expo(int base,int power,int modulo=mod){
    base%=modulo;
    if (base<0) base+=modulo;
    ll x=base,cnt=power,ans=1;
    while(cnt){
        if (cnt&1) ans=(ans*x)%modulo;
        x=(x*x)%modulo;
        cnt>>=1;
    }
    // int tmp=ans;
    return ans;
}
 
void __print(int x) {cerr << x;}
void __print(long x) {cerr << x;}
void __print(long long x) {cerr << x;}
void __print(unsigned x) {cerr << x;}
void __print(unsigned long x) {cerr << x;}
void __print(unsigned long long x) {cerr << x;}
void __print(float x) {cerr << x;}
void __print(double x) {cerr << x;}
void __print(long double x) {cerr << x;}
void __print(char x) {cerr << '\'' << x << '\'';}
void __print(const char *x) {cerr << '\"' << x << '\"';}
void __print(const string &x) {cerr << '\"' << x << '\"';}
void __print(bool x) {cerr << (x ? "true" : "false");}
 
template<typename T, typename V>
void __print(const pair<T, V> &x) {cerr << '{'; __print(x.first); cerr << ','; __print(x.second); cerr << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cerr << '{'; for (auto &i: x) cerr << (f++ ? "," : ""), __print(i); cerr << "}";}
void _print() {cerr << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cerr << ", "; _print(v...);}
#ifndef ONLINE_JUDGE
#define debug(x...) cerr << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif
 
const int INF = (int)1e9;
//=========================CODE STARTS HERE=============================//
 
 
 
int main() {
 
	fast_cin();
 
	ll n;
	cin >> n;
	ll k;
	cin >> k;
	
	if (k == 1) {
		cout << 0 << endl;
		return 0;
	}
	
	vl arr(n);
	vl pre(n + 1);
	pre[0] = 0;
	ll sum = 0;
	fo(i, n){
		cin >> arr[i];
		sum += arr[i];
		pre[i + 1] = sum;
	}
	
	vl fin(n + 1);
	fin[0] = 0;
	fo(i, n + 1) {
		fin[i] = (pre[i] - i) % (k);
	}
	debug(fin);
	map<ll, ll> count;

	count[0]++;
	ll ans = 0;
	for (int i = 1; i < n + 1; ++i) {
		ans += count[fin[i]];
		count[fin[i]]++;
		if (i - k + 1 >= 0) {
			count[fin[i - k + 1]]--;
		}
	}
	
	cout << ans << endl;
	return 0;
}


Measured memory_bytes: 17508