#include<bits/stdc++.h>
#include <algorithm>
#define lli long long int
#define li long int
#define mod 1000000007
#define ld long double
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define REP(i,a,b) for (int i = a; i < b; i++)
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);
    cin.tie(NULL);

    int n;
    cin>>n;

    map<int,int> m;

    int k;
    cin>>k;

    int arr[n];
    for (int i = 0; i < n; i++)
    {
        cin>>arr[i];
    }


    for (int i = 0; i < n-k+1; i++)
    {   int ans=0;
        for (int j = 0; j < k; j++)
        {
           ans=ans+arr[j];
        }
        m.insert({ans,i+1});
    }

    cout<<m.size()<<endl;

    for (auto pr:m)
    {
        cout<<pr.first<<" "<<pr.second<<endl;
    }

return 0;
}