#include<iostream>

using namespace std;
#define repeat(i, n) for(int i=0; i<(n); i++)
int memo[51][101][101];
const int inf=1e8;

int main(){

   int gx, gy, N, F;
   cin>> gx>> gy>> N>> F;
   int dx[N], dy[N], c[N];
   repeat(i, N) cin>> dx[i]>> dy[i]>> c[i];

   repeat(i, 51){
      repeat(x, 101){
         repeat(y, 101){
            if(x==0&&y==0) memo[i][x][y]=0;
            else memo[i][x][y]=inf;
         }
      }
   }

   repeat(i, N){
      repeat(x, gx+1){
         repeat(y, gy+1){
            memo[i+1][x][y]=min(memo[i+1][x][y], memo[i][x][y]);
            if(memo[i][x][y]==inf) continue;
            if(x+dx[i]>gx||y+dy[i]>gy) continue;
            if(c[i]>(dx[i]+dy[i])*F) continue;
            memo[i+1][x+dx[i]][y+dy[i]]
            =min(memo[i+1][x+dx[i]][y+dy[i]], memo[i][x][y]+c[i]);
         }
      }
   }

   int C=inf;
   repeat(x, gx+1){
      repeat(y, gy+1){
         if(memo[N][x][y]==inf) continue;
         int _c=F*((gx-x)+(gy-y));
         _c+=memo[N][x][y];
         C=min(C, _c);
      }
   }

   cout<< C<< endl;

   return 0;
}