#include <bits/stdc++.h>

using namespace std;
const int MAXN = 2e5 + 10;
double arr[105][105][105];
double f(int a, int b, int c) {
  if (arr[a][b][c]) return arr[a][b][c];
  if (a == 100 || b == 100 || c == 100) return 0.0;
  double ans = 0.0;
  ans += (f(a + 1, b, c) + 1) * a / (a + b + c);
  ans += (f(a, b + 1, c) + 1) * b / (a + b + c);
  ans += (f(a, b, c + 1) + 1) * c / (a + b + c);
  arr[a][b][c] = ans;
  return ans;
}
int main() {
  double a, b, c;
  cin >> a >> b >> c;
  double res = f(a, b, c);
  cout << fixed << setprecision(9) << res;
}

#include <bits/stdc++.h>
using namespace std;
#define REP(i,n) for (int i = 0; i < (n); ++i)
template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b;return true;}return false;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b;return true;}return false;}
using ll = long long;
using P = pair<int,int>;
using Pl = pair<long long,long long>;
using veci = vector<int>;
using vecl = vector<long long>;
using vecveci = vector<vector<int>>;
using vecvecl = vector<vector<long long>>;
const int MOD = 1000000007;
const double pi = acos(-1);
ll gcd(ll a, ll b) {if(b == 0) return a; else return gcd(b,a%b);}
ll lcm(ll a, ll b) {return a*b/gcd(a,b);}
 
int main() {
    int N; cin >> N;
    ll X; cin >> X;
    vecl A(N);
    REP(i,N) {
        ll v,p; cin >> v >> p;
        A[i] = v*p;
    }
    ll total = 0;
    REP(i,N) {
        total += A[i];
        if(total > X*100) {
            cout << i+1 << endl;
            return 0;
        }
    }
    cout << -1 << endl;
    return 0;
}