#include <bits/stdc++.h>
#pragma GCC target ("avx2")
#pragma GCC optimization ("O3")
#pragma GCC optimization ("unroll-loops")
#pragma comment(linker, "/stack:200000000")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#pragma GCC target("fpmath=387") //extra precision   
#define debug_input freopen("stdin.in", "r", stdin)
#define debug_output freopen("stdout.out", "w", stdout)
#define FOR(i, a, b) for(ll i = a; i <= b; i++)
#define FORALL(i, n) for(ll i = 0; i < n; i++)
#define FORD(i, a, b) for(ll i = a; i >= b; i--)
#define SORT(a) sort(a.begin(), a.end())
#define REV(a) reverse(a.begin(), a.end())
#define NP(a) next_permutation(a.begin(), a.end())
#define ALL(a) a.begin, a.end()
#define mp make_pair
#define pb push_back
#define endl '\n'
using namespace std;

typedef long long ll;
typedef unsigned long long ull;

const ll N = 1e5 + 5;
const ll mod = 1e9 + 7;
const ll inf = 1e18;
const double pi = 3.141592653589793;
const ll dr[4] = {-1,0,1,0}, dc[4] = {0,1,0,-1};

void solve() {
	ll n, x;
	cin >> n >> x;

	ll total = 0;
	FOR(i, 1, n) {
		ll v, p;
		cin >> v >> p;

		total += v * p;
		if(total > 100 * x) {
			cout << i << endl;
			return;
		}
	}
	cout << -1 << endl;
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);

	ll t = 1; 
	//cin >> t;
	while(t--) {
		solve();
	} 
	return 0;
}
#include <bits/stdc++.h>
#define rep(i, l, r) for (int i = (l); i < (r); i++)
using namespace std;

typedef long long ll;

map<vector<int>, ll> mp;

ll MOD = 1e9 + 7;

ll mod_pow(ll x, ll n, ll mod) {
    ll res = 1;
    while (n > 0) {
        if (n & 1) res = res * x % mod;
        x = x * x % mod;
        n >>= 1;
    }
    return res;
}

int main() {
    int N, M, K;
    cin >> N >> M >> K;
    if (N > M + K) {
        cout << 0 << endl;
        return 0;
    }
    vector<ll> f(N + M + 1, 1);
    rep(i, 0, N + M) f[i + 1] = (f[i] * (i + 1)) % MOD;
    ll ans = f[N + M];
    ans *= mod_pow(f[N], MOD - 2, MOD);
    ans %= MOD;
    ans *= mod_pow(f[M], MOD - 2, MOD);
    ans %= MOD;
    //cout << "ans0=" << ans << endl;
    if (K < N && N - K - 1 >= 0) {
        ll x = f[N + M];
        x *= mod_pow(f[M + K + 1], MOD - 2, MOD);
        x %= MOD;
        x *= mod_pow(f[N - K - 1], MOD - 2, MOD);
        x %= MOD;
        //cout << "x=" << x << endl;
        ans = (ans + MOD - x) % MOD;
    }
    cout << ans << endl;
}