#include <bits/stdc++.h>

using namespace std;

#define int long long
// #define double long double
#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORR(i, a, b) for(int i = (a); i > (b); --i)
#define REP(i, n) for(int i = 0; i < (n); ++i)
#define REPR(i, n) for(int i = n; i >= 0; i--)
#define FOREACH(x, a) for(auto &(x) : (a))
#define VECCIN(x)                                                              \
    for(auto &youso_ : (x)) cin >> youso_
#define bitcnt(x) __builtin_popcount(x)
#define lbit(x) __builtin_ffsll(x)
#define rbit(x) __builtin_clzll(x)
#define SZ(x) ((long long)(x).size())
#define fi first
#define se second
#define All(a) (a).begin(), (a).end()
#define rAll(a) (a).rbegin(), (a).rend()
#define cinfast() cin.tie(0), ios::sync_with_stdio(false)
#define PERM(c)                                                                \
    sort(All(c));                                                              \
    for(bool cp = true; cp; cp = next_permutation(All(c)))
#define MKORDER(n)                                                             \
    vector<int> od(n);                                                         \
    iota(All(od), 0LL);

template <typename T = long long> inline T IN() {
    T x;
    cin >> x;
    return (x);
}
inline void CIN() {}
template <class Head, class... Tail>
inline void CIN(Head &&head, Tail &&... tail) {
    cin >> head;
    CIN(move(tail)...);
}
#define CCIN(...)                                                              \
    char __VA_ARGS__;                                                          \
    CIN(__VA_ARGS__)
#define DCIN(...)                                                              \
    double __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define LCIN(...)                                                              \
    long long __VA_ARGS__;                                                     \
    CIN(__VA_ARGS__)
#define SCIN(...)                                                              \
    string __VA_ARGS__;                                                        \
    CIN(__VA_ARGS__)
#define Yes(a) cout << (a ? "Yes" : "No") << "\n"
#define YES(a) cout << (a ? "YES" : "NO") << "\n"
#define Printv(v)                                                              \
    {                                                                          \
        FOREACH(x, v) { cout << x << " "; }                                    \
        cout << "\n";                                                          \
    }
template <typename T = string> inline void eputs(T s) {
    cout << s << "\n";
    exit(0);
}
template <typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *)array, (T *)(array + N), val);
}

template <typename T> using PQG = priority_queue<T, vector<T>, greater<T>>;
template <typename T> using PQ = priority_queue<T>;

typedef long long ll;
typedef vector<ll> VL;
typedef vector<VL> VVL;
typedef pair<ll, ll> PL;
typedef vector<PL> VPL;
typedef vector<bool> VB;
typedef vector<double> VD;
typedef vector<string> VS;

const int INF = 1e9;
const int MOD = 1e9 + 7;
// const int MOD = 998244353;
const ll LINF = 1e18;
const double PI = atan(1.0) * 4.0;
const ll dw[] = {1, 1, 0, -1, -1, -1, 0, 1};
const ll dh[] = {0, 1, 1, 1, 0, -1, -1, -1};
#define PI 3.141592653589793238

const int MAX_SIZE = 1000010;
class mint {
  public:
    static ll MOD;
    ll x;
    mint() : x(0) {}
    mint(ll x) : x(x % MOD) {}
    mint &fix() {
        x = (x % MOD + MOD) % MOD;
        return *this;
    }
    mint operator-() const { return mint(0) - *this; }
    mint &operator+=(const mint &a) {
        if((x += a.x) >= MOD) {
            x -= MOD;
        }
        return *this;
    }
    mint &operator-=(const mint &a) { return *this += -a; }
    mint &operator*=(const mint &a) {
        (x *= a.x) %= MOD;
        return *this;
    }
    mint &operator/=(const mint &a) { return (*this *= power(MOD - 2)); }
    mint operator+(const mint &a) const { return mint(*this) += a; }
    mint operator-(const mint &a) const { return mint(*this) -= a; }
    mint operator*(const mint &a) const { return mint(*this) *= a; }
    mint operator/(const mint &a) const { return mint(*this) /= a; }
    bool operator<(const mint &a) const { return x < a.x; }
    bool operator==(const mint &a) const { return x == a.x; }
    const mint power(ll N) {
        if(N == 0) {
            return 1;
        } else if(N % 2 == 1) {
            return *this * power(N - 1);
        } else {
            mint half = power(N / 2);
            return half * half;
        }
    }
};
ll mint::MOD = 1e9 + 7;
istream &operator>>(istream &stream, mint &a) { return stream >> a.x; }
ostream &operator<<(ostream &stream, const mint &a) { return stream << a.x; }
mint inv[MAX_SIZE];
mint fact[MAX_SIZE];
mint factinv[MAX_SIZE];
void init() {
    inv[1] = 1;
    for(int i = 2; i < MAX_SIZE; i++) {
        inv[i] = (-inv[mint::MOD % i]) * (mint::MOD / i);
    }
    fact[0] = factinv[0] = 1;
    for(int i = 1; i < MAX_SIZE; i++) {
        fact[i] = mint(i) * fact[i - 1];
        factinv[i] = inv[i] * factinv[i - 1];
    }
}
mint choose(int n, int k) {
    if(n >= 0 && k >= 0 && n - k >= 0) {
        return fact[n] * factinv[k] * factinv[n - k];
    }
    return 0;
}
ll gcd(ll x, ll y) { return y ? gcd(y, x % y) : x; }

signed main() {
    LCIN(N, K);
    VL A(N);
    VECCIN(A);
    VL sum(N + 1);
    REP(i, N) { sum[i + 1] = (sum[i] + A[i] - 1) % K; }
    ll ans = 0;
    map<ll, int> mp;
    for(int i = 0; i <= N; i++) {
        if(i >= K) mp[sum[i - K]]--;
        ans += mp[sum[i]];
        mp[sum[i]]++;
    }
    cout << ans << "\n";
}


Measured memory_bytes: 39296