//qoj7078
#include <bits/stdc++.h>
using namespace std;

const int N = 2e5 + 10, B = 1000;
typedef long long ll;
int n;
ll mx;
pair<ll, ll> a[N];

int read(){
    int x = 0;
    char ch = getchar();
    while(ch < '0' || ch > '9') ch = getchar();
    while(ch >= '0' && ch <= '9'){
        x = x * 10 + ch - '0';
        ch = getchar();
    }
    return x;
}

#define calc(i, j) (a[i].first * ((a[i].second - 1) / a[j].first))

struct sqrtTech{
    ll val[N], Bval[N], nx[N], Bnx[N];
    int inb[N], le[N], ri[N];
    void init(){
        memset(val, 0x3f, sizeof(val));
        memset(Bval, 0x3f, sizeof(Bval));
        memset(Bnx, 0x3f, sizeof(Bnx));
        memset(nx, 0x3f, sizeof(nx));
        for(int i = 1; i <= mx; ++ i){
            inb[i] = (i - 1) / B + 1;
            if(inb[i] != inb[i-1]){
                le[inb[i]] = i;
                ri[inb[i]-1] = i-1;
            }
        }
        ri[inb[mx]] = mx;
    }
    void mdf(int x, ll v){
        if(val[x] <= v){
            return;
        }
        val[x] = min(val[x], v);
        Bval[inb[x]] = min(Bval[inb[x]], v);
        int bl = inb[x];
        nx[ri[bl]] = val[ri[bl]];
        for(int i = ri[bl] - 1; i >= le[bl]; -- i){
            nx[i] = min(nx[i+1], val[i]);
        }
        for(int i = inb[mx]; i >= 1; -- i){
            Bnx[i] = min(Bval[i], Bnx[i+1]);
        }
    }
    ll qry(int l){
        return min(nx[l], Bnx[inb[l]+1]);
    }
} sq;

int main(){
    n = read();
    a[0].first = read();
    for(int i = 1; i <= n; ++ i){
        a[i].first = read();
        a[i].second = read();
        mx = max(mx, a[i].first);
    }
    mx = max(mx, a[0].first);
    mx = 200000;
    sq.init();
    sort(a + 1, a + n + 1);
    if(a[0].first >= a[n].first){
        ll ans = 0;
        for(int i = 1; i <= n; ++ i){
            ans += calc(i, 0);
        }
        printf("%lld\n", ans);
        return 0;
    }
    int st = 0;
    ll f = 0;
    for(int i = 1; i <= n; ++ i){
        if(a[i].first > a[0].first){
            st = i;
            break;
        }
    }
    sq.mdf(a[0].first, 0);
    for(int i = st; i <= n; ++ i){
        int pp = a[i].second - 1;
        f = 1e18;
        int BB = 1000;
        for(int j = 1; j <= min(pp, BB); ++ j){
            f = min(f, sq.val[j] + a[i].first * (pp / j));
        }
        for(int l = BB+1, r; l <= pp; l = r + 1){
            r = pp / (pp / l);
            f = min(f, sq.qry(l) + a[i].first * (pp / l));
        }
        if(pp < mx) f = min(f, sq.qry(pp+1));
        f -= calc(i, n);
        sq.mdf(a[i].first, f);
    }
    for(int i = 1; i <= n; ++ i){
        f += calc(i, n);
    }
    printf("%lld\n", f);
    return 0;
}