#include <bits/stdc++.h>

using namespace std;

const int INF = 1000000000;

int main()
{
    int n, m;
    cin >> n >> m;

    vector <pair<int, int> > a(n);
    vector <int> ini(n), fin(n);

    for(int i=0; i<n; i++)
    {
        cin >> a[i].first >> a[i].second;
        ini[i] = a[i].first-a[i].second;
        fin[i] = a[i].first+a[i].second;
    }

    vector <int> DP(m+1, INF);
    DP[0] = 0;

    for(int i=1; i<=m; i++)
    {
        for(int j=0; j<n; j++)
        {
            if(ini[j] <= i && i <= fin[j])
            {
                DP[i] = min(DP[i], DP[i-1]);
            }
            else
            {
                if(i < ini[j])
                {
                    DP[i] = min(DP[i], DP[i-1]+ini[j]-i);
                }
                else
                {
                    int x = i-fin[j];
                    DP[i] = min(DP[i], DP[max(0, ini[j]-x-1)]+x);
                }
            }
        }
    }

    cout << DP[m] << endl;

    return 0;
}