#include<iostream>
#include<cstdio>
#include<cstring>
#include<cmath>
#include<algorithm>
#include<vector>
using namespace std;
const int maxn=300+5;

int m,f,n,c;
int b[maxn],p[maxn];
int dp1[maxn][maxn][maxn],dp2[maxn][maxn][maxn];

int main() {
    ios::sync_with_stdio(false);
    memset(dp1,0x7f,sizeof(dp1));
    memset(dp2,0x7f,sizeof(dp2));
    dp1[0][0][0]=0;dp2[0][0][0]=0;
    cin>>m>>f>>n>>c;
    for(int i=1; i<=n; i++)
        cin>>b[i]>>p[i];

    for(int i=1; i<=n; i++) {
        for(int j=0; j<=m; j++) {
            for(int k=0; k<=f; k++) {
                dp1[i][j][k]=min(dp1[i-1][j][k],min(dp1[i-1][max(0,j-b[i])][k]+p[i],dp1[i-1][j][max(0,k-b[i])]+p[i]));
                if(b[i]>=2 && j>=1 && k>=1 && i>=1)
                    dp2[i][j][k]=min(dp2[i][j][k],dp1[i-1][j-1][k-1]+p[i]);
                dp2[i][j][k]=min(dp2[i-1][j][k],min(dp2[i-1][max(0,j-b[i])][k]+p[i],dp2[i-1][j][max(0,k-b[i])]+p[i]));
            }
        }
    }
    int ans=2147483647;
    ans=min(dp1[n][m][f],dp2[n][m][f]);
    //if(ans>=2139062143)
    //  cout<<"impossible";
    else
        cout<<ans;
    return 0;
}