//#pragma GCC optimize("O3")
#include <bits/stdc++.h>
//#define int int64_t
#define all(x) (x).begin(), (x).end()
#define out(x) return void(cout << x << endl)
#define OUT(x) ((cout << x), exit(0))
using namespace std;
typedef long double db;
const int64_t INF = (int64_t)(2e18);
const int inf = (int)(1e9 + 7);
const db eps = (db)1e-9;
//------------------------------------------//

inline bool eq(db a, db b) { return abs(a - b) < eps; }
vector<pair<db, db>> ar;
vector<db> k;

bool check(db mid, int m, db t) {
    fill(all(k), 0);
    for (int i = 0; i < ar.size() && !eq(mid, 0); ++i) {
        k[i] = (min(mid, ar[i].first));
        mid -= k[i];
    }

    int i = (int)k.size() - 1;
    int day = 1;
    while (true) {
        db cur = t;
        while (!eq(cur, 0)) {
            db mult = pow(1 + ar[i].second, day);
            db now = min(k[i], cur / mult);
            k[i] -= now;
            cur -= now * mult;
            if (eq(k[i], 0)) --i;
            if (i < 0)
                return true;
        }


        ++day;
        if (day > min(m, 100))
            return false;
    }

}


int32_t main()
{
    ios_base::sync_with_stdio(false);
    cout << fixed << setprecision(40);
    cin.tie(nullptr);

#ifdef _MY
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif

    int n, m;
    int tmpt;
    db t;
    cin >> n >> m >> tmpt;
    t = tmpt;

    k.resize(n);
    ar.resize(n);
    for (auto& it : ar) {
        int a;
        cin >> a; it.first = a;
        cin >> a; it.second = a / 1000000.0;
    }

    sort(all(ar), [](pair<db, db> a, pair<db, db> b) {return a.second < b.second; });

    db l = 0;
    db r = 0;
    for (auto& it : ar) r += it.first;

    for (int i = 0; i < 100; ++i) {
        if (eq(l, r)) break;
        db mid = (l + r) / 2;
        if (check(mid, m, t)) l = mid;
        else r = mid;
    }

    cout << r;

    return 0;
}