#include<stdio.h>
#define min(a,b) ((a)<(b))?(a):(b)

int main(int argc, char const *argv[]){
	long x,y,n,f,cx[50],cy[50],cc[50],i,mc[101][101][2],j,k;
	scanf("%ld %ld %ld %ld",&x,&y,&n,&f);
	for(i=0;i<n;i++){
		scanf("%ld %ld %ld",&cx[i],&cy[i],&cc[i]);
	}
	for(i=0;i<=x;i++){
		for(j=0;j<=y;j++){
			mc[i][j][0]=f*(i+j);
		}
	}
	for(i=0;i<n;i++){
		for(j=0;j<=x;j++){
			for(k=0;k<=y;k++){
				if(0<=j-cx[i] && 0<=k-cy[i]){
					mc[j][k][(i+1)%2]=min(mc[j][k][i%2],mc[j-cx[i]][k-cy[i]][i%2]+cc[i]);
				}else{
					mc[j][k][(i+1)%2]=mc[j][k][i%2];
				}
			}
		}
	}
	printf("%ld\n",mc[x][y][n%2]);
	return 0;
}