#include <stdio.h>
#include <string.h>
#include <math.h>
#include <stdlib.h>
//Complete the following function.

int find_nth_term(int n, int a, int b, int c) {
    int sum = 0;
    if (n==1){
        sum = a;
    }
    else if (n==2){
        sum = b;
    }
    else if (n==3){
        sum = c;
    }
    else if (n>3){
        for (int i=n-3; i<n; i++){
            sum += find_nth_term(i, a, b, c);
        }
    }
    return sum;
}

int main() {
    int n, a, b, c;
  
    scanf("%d %d %d %d", &n, &a, &b, &c);
    int ans = find_nth_term(n, a, b, c);
 
    printf("%d", ans); 
    return 0;
}