import java.util.Scanner;


public class task9 {


    public static void main(String[] args) {
          Scanner sc = new Scanner(System.in);
          int n = sc.nextInt();
          int m = sc.nextInt();
          int x = sc.nextInt();
          int y = sc.nextInt();
          int cl = 0;
          int stroka =1;
          int[][] mas = new int[n][m];
         for(int i=0;i<n;i++){
             if(stroka%2==1){
                 for(int j=0;j<m;j++){
                 mas[i][j]=cl;
                 cl++;

                 }
                 stroka++;
             }
             else{
                 for(int j=m-1;j>=0;j--){
                 mas[i][j]=cl;
                 cl++;
                 }
                 stroka++;
             }
         }
        System.out.println(mas[x-1][y-1]);

            }


}

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Edited by author 07.05.2019 14:29

Edited by author 07.05.2019 14:36