#include <bits/stdc++.h>
#define PI pair<int,int>
#define F first
#define S second
#define PB push_back
#define MP make_pair
#define REP(i,a,b) for(int i = a; i <= b; ++i)
#define ll long long

using namespace std;
const int N = 1e5 + 9, Inf = 0x3f3f3f3f;
int n, s, t, c, x;
int v[N];
ll ans;

template <typename T, typename comp = less<int>, int undef = Inf>
class qdeque
{
private:
    deque<pair<T,int> > dq;
    comp cmp;
public:
    void push(int val,int i)
    {
        while(!dq.empty() && ! cmp(dq.back().F + (i - dq.back().S) * s, val))
            dq.pop_back();
        dq.PB(MP(val,i));
    }
    T query(int i)
    {
        while(!dq.empty() && i - dq.front().S > t)
            dq.pop_front();

        if(dq.empty()) return undef;
        return dq.front().F + (i - dq.front().S) * s;
    }
};

int main()
{
    freopen("branza.in", "r", stdin);
    freopen("branza.out", "w", stdout);

    qdeque<int> q;

    cin >> n >> s >> t;
    REP(i,1,n)
    {
        cin >> c >> x;
        ans += min(1LL * c, 1LL * q.query(i)) * x;
        q.push(c,i);
    }

    cout << ans;
    return 0;
}