#include<stdio.h>

int minim(int x,int y){if(x < y){return x;}return y;}

int main(void){
	int dp[128][128];
	int gx,gy,n,f;
	int x,y,c;
	int t,i,j,jud;
	scanf("%d%d%d%d",&gx,&gy,&n,&f);
	for(i = 0;i <= 127;i++){
		for(j = 0;j <= 127;j++){
			dp[i][j] = f*(i+j);
		}
	}
	for(t = 1;t <= n;t++){
		scanf("%d%d%d",&x,&y,&c);
		for(i = 127;i >= 0;i--){
			for(j = 127;j >= 0;j--){
				if(i+x <= 127 && j+y <= 127){
					dp[i+x][j+y] = minim(dp[i+x][j+y],dp[i][j]+c);
				}
			}
		}
		for(i = 0;i <= 127;i++){
			for(j = 0;j <= 127;j++){
				if(i == 0){jud = dp[i][j-1];}
				else if(j == 0){jud = dp[i-1][j];}
				else{jud = minim(dp[i][j-1],dp[i-1][j]);}
				dp[i][j] = minim(dp[i][j],jud+f);
			}
		}
	}
	printf("%d\n",dp[gx][gy]);
	return 0;
}