#include <bits/stdc++.h>
using namespace std;
#define fi first
#define se second
#define ll long long
#define mp(x, y) make_pair(x, y)
#define sz(v) ((int) (v).size())
#define all(v) (v).begin(), (v).end()
#define MASK(i) (1LL << (i))
#define BIT(x, y) (((x) >> (y)) & 1)
#define pb push_back
#define max_rng *max_element
#define min_rng *min_element
#define rep(i, n) for(int i = 1, _n = (n); i <= _n; ++i)
#define forn(i, a, b) for(int i = (a), _b = (b); i <= _b; ++i)
#define ford(i, a, b) for(int i = (a), _b = (b); i >= _b; --i)
template <class X, class Y>
inline bool maximize(X &x, Y y) {
return (x < y ? x = y, true : false);
}
template <class X, class Y>
inline bool minimize(X &x, Y y) {
return (x > y ? x = y, true : false);
}
template <class X>
inline void compress(vector<X> &a) {
sort(all(a));
a.resize(unique(all(a)) - a.begin());
}
int ctz(ll x) { return __builtin_ctzll(x); }
int lg(ll x) { return 63 - __builtin_clzll(x); }
int popcount(ll x) { return __builtin_popcount(x); }
mt19937_64 rng(chrono::high_resolution_clock::now().time_since_epoch().count());
ll rand(ll l, ll r) {
return l + abs((ll) rng()) % (r - l + 1);
}
const ll oo = (ll) 1e17;
const int inf = (ll) 1e9 + 7, mod = (ll) 1e9 + 7;
const int N = 5e5 + 5, M = 250005, BASE = 307, LOG = 23;
void add(int &x, int y) { x += y; if (x >= mod) x -= mod; }
void sub(int &x, int y) { x -= y; if (x < 0) x += mod; }
int n; ll s;
int par[N], cost[N];
namespace one {
bool one() {
rep(i, n) if (par[i] && par[i] != i - 1)
return false;
return true;
}
vector<int> arr[N];
ll apply(ll base, int type) {
ll ans = base, res = base;
forn(i, 0, sz(arr[type]) - 1) {
ans += cost[arr[type][i]];
if (ans < 0) break;
maximize(res, ans);
}
return res;
}
void solve() {
int cnt = 0;
forn(i, 1, n) if (!par[i]) {
cnt++;
forn(j, i, n) if (par[i]) {
arr[cnt].pb(j);
} else break;
}
ll Max = s;
priority_queue<ll> pq;
pq.push(s);
while (sz(pq)) {
ll top = pq.top(); pq.pop();
forn(i, 1, cnt) {
if (maximize(Max, apply(top, i))) {
pq.push(Max);
}
}
}
cout << Max;
return;
}
}
int main(void) {
ios_base::sync_with_stdio(0);
cin.tie(0); cout.tie(0);
cin >> n >> s;
rep(i, n) cin >> cost[i] >> par[i];
{
if (one::one()) return one::solve(), 0;
}
return 0;
}
