#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 arr[30] = {a,b,c};
    int i= 0;
    int sum=0;
    int sum1 = 0;
    
    if(n==1){return a;}
    else if(n==2){return b;}
    
    else if(n==3){return c;}
    
    else{
        for(;i<n -3;i++){
            sum =  arr[i+2] + arr[i+1] + arr[i];
            arr[i + 3] = sum;
            sum1 = arr[i + 3];        
        }
        
        return sum1;
    }

}

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;
}