#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
 
int main() {
	const int L = 5;
	vector<int> v = { 1, 10, 11, 2 };
	const int N = v.size();
 
	sort(v.begin(), v.end());
// the algo tries to include elements in interval of length 2 * L
int ans = 0;
int first = 0; 
for(int i = 1; i < N; ++i) {
    if(v[i] - v[first] > 2 * L) { // if we can't include i-th element 
        ans++;                    // into the current interval   
        first = i;                // the algo construct new 
    }
}
ans++;
printf("%d", ans);
}

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