Rope folding

/// https://www.hackerrank.com/contests/simulacro-oia-4-1/challenges/problem-0-rope-folding

#include <iostream>
#include <vector>
using namespace std;

int main()
{
    int n, l, c=0;
    cin>>n>>l;

    vector<bool> v (l+1);

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

    for (float q=1; q<l; q+=(0.5))
    {
        int centro = 2*q, ini=centro/2, fin=centro/2;
        if ( centro%2 == 1 )
            ini++; ///cout<<q<<" : "<<ini<<" "<<fin<<endl;

        bool es = true;

        while ( ini>0 && fin<l )
        {
            ini--;
            fin++;

            if ( v[ini] != v[fin] )
                es = false;
        }

        if (es)
            c++;
    }

    cout<<c;

    return 0;
}