Bai1

#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

// Recursive function to return gcd of a and b
int GCD(int a, int b){
    return b == 0 ? a : GCD(b, a % b);
}

int main(){
    long long  n, k;
    cin >> n >> k;
    vector <long long> a(n);
    vector <long long> prefixGCD(n);
    for (long long i = 0; i < n; i++) {
        cin >> a[i];
    }
    long long gcd_max = a[0];
    long long start = 0, end = 0;

//______________O(kN)_________________//

    for (long long i = 0; i <= n-k; i++) {
        long long gcd = 0;
        for (long long j = i; j < i+k ; ++j){
            gcd = GCD(gcd, a[j]);
            printf("%3lld -> gcd %3lld; ",a[j],gcd);
        }
        if (gcd > gcd_max){
            gcd_max = gcd;
            start = i;
            end = i+k;
        }
        cout<<" --> "<<gcd_max<<endl;
    }

    cout << gcd_max <<endl;
    cout << start << " " << end << endl;
    return 0;
}