#include <iostream>
#include <algorithm>
using namespace std;

int main(){
    int Gx,Gy,N,F;
    cin>>Gx>>Gy>>N>>F;
    int DP[Gx+1][Gy+1];
    for(int y=0;y<=Gy;y++){
        for(int x=0;x<=Gx;x++){
            DP[x][y]=(x+y)*F;
        }
    }
    for(int i=0;i<N;i++){
        int x,y,c;
        cin>>x>>y>>c;
        for(int Y=0;Y+y<=Gy;Y++){
            for(int X=0;X+x<=Gx;X++){
                DP[X+x][Y+y]=min(DP[X+x][Y+y],DP[X][Y]+c);
            }
        }
    }
    cout<<DP[Gx][Gy]<<endl;
    return 0;
}