/*

 ∧＿∧
( ･ω･｡)つ━☆・*。
⊂　 ノ 　　　・゜
しーＪ　　 Accepted

*/



// #pragma GCC optimize("O3")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>

#define ll long long
#define all(x) begin(x), end(x)
#define x first
#define y second
#define int long long

using namespace std;
using namespace __gnu_pbds;

typedef long double ld;
template<typename T>
using kawaii_set = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;

const ld PI = atan2(0, -1);

void seriy() {
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    cout << fixed << setprecision(14);
    #ifdef _offline
        freopen("input.txt", "r", stdin);
        freopen("output.txt", "w", stdout);
    #endif
}

const int MAXN = 1e6 + 10;
const int MAXM = 600;
const int INF = 1e9;
const int BASE = 47;
const int MOD = 43200;
const int MAXLOG = 21;

vector<vector<int>> dp;

int get(int i, int v, int tl, int tr, int l, int r) {
    if(tl > r || tr < l) {
        return INF;
    }
    if(tl >+ l && tr <= r) {
        return dp[i][v];
    }
    int tm = (tl + tr) >> 1;
    int left = get(i, v * 2 + 1, tl, tm, l, r);
    int right = get(i, v * 2 + 2, tm + 1, tr, l, r);
    return min(left, right);
}

void update(int i, int v, int tl, int tr, int pos, int val) {
    if(tl > pos || tr < pos) {
        return;
    }
    if(tl == tr) {
        dp[i][v] = min(dp[i][v], val);
        return;
    }
    int tm = (tl + tr) >> 1;
    update(i, v * 2 + 1, tl, tm, pos, val);
    update(i, v * 2 + 2, tm + 1, tr, pos, val);
    dp[i][v] = min(dp[i][v * 2 + 1], dp[i][v * 2 + 2]);
}

signed main() {
    seriy();
    int n, m;
    cin >> n >> m;
    vector<pair<int, int>> a(n);
    for(int i = 0; i < n; i++) {
        cin >> a[i].x >> a[i].y;
    }
    a.push_back({1, 0});
    a.push_back({m, 0});
    sort(all(a));
    dp.resize(a.size(), vector<int>(4 * (m + 2), INF));
    dp[0][0] = 0;
    for(int i = 1; i < dp.size(); i++) {
        for(int j = 0; j < m + 1; j++) {
            int mn = get(i, 0, 0, m, max(a[i].x - a[i - 1].x - j, 0ll), m);
            update(i, 0, 0, m, j, mn + max(j - a[i].y, 0ll));
        }
    }
    cout << get(dp.size() - 1, 0, 0, m, 0, 0);
    return 0;
}