// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops", "omit-frame-pointer", "inline")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,popcnt,abm,mmx,avx,avx2,fma,tune=native")
// #pragma GCC option("arch=native", "no-zero-upper") // Enable AVX

/// UH Top
#include <bits/stdc++.h>
#define db(x) cerr << #x << ':' << (x) << '\n';
#define all(v) (v).begin(), (v).end()
#define allr(v) (v).rbegin(), (v).rend()
// #define int ll
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
// typedef __int128_t int128;
typedef pair<ll, ll> pii;
typedef pair<ld, ll> pdi;
typedef pair<ld, ld> pdd;
typedef pair<ld, pdd> pdp;
typedef pair<string, ll> psi;
typedef pair<ll, string> pls;
typedef pair<string, string> pss;
typedef pair<ll, pii> pip;
typedef pair<pii, pii> ppp;
typedef complex<ld> point;
typedef vector<point> polygon;
typedef vector<ll> vi;
typedef pair<point, int> ppi;
#define prec(n)        \
    cout.precision(n); \
    cout << fixed
const ll mod = (1e9 + 7);
const ld eps = (1e-9);
const ll oo = (ll)(1e18 + 5);
#define pi acos(-1)
#define MAXN (ll)(4e6 + 5)

bitset<MAXN> dp;

int32_t main()
{
    ios_base::sync_with_stdio(0);
    cin.tie(0);

    // bitset<10> test;
    // for(int i=0;i<10;i++)
    //     test[i]=1;
    // cout << ((test>>3)<<3) << '\n';

    int n,v,c;
    cin >> n >> v >> c;
    vector<pii> ps;
    ll sum=0;
    for(int i=0;i<n;i++)
    {
        int x,d;
        cin >> x >> d;
        ps.push_back(pii(d*v+x*c,x));
        sum+=x;
    }

    sort(all(ps));

    // db("xxx")
    dp[0]=1;
    for(int i=0;i<n;i++)
    {
        int x=ps[i].second;
        int d=(ps[i].first-x*c)/v;

        int lim=min((d*v-1)/c,(int)MAXN-1);
        // cout << lim << ' ' << d << ' ' << x << ' ' << '\n';
        dp=(dp|(((dp<<(MAXN-lim-1))>>(MAXN-lim-1))<<x));
        // cout << dp << '\n';
    }
    // db("xxx")

    int ma=0;
    for(int i=0;i<MAXN;i++)
        if(dp[i])
            ma=i;
    sum+=(ma)*(c-1);
    cout << sum << '\n';

    return 0;   
}