#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 term, t1 = a, t2 = b, t3 = c;
    if (n == 1)
        term = t1;
    else if (n == 2)
        term = t2;
    else if (n == 3)
        term = t3;
    else {
        for (int i = 4; i <= n; i++) {
            term = t1 + t2 + t3;
            t1 = t2;
            t2 = t3;
            t3 = term;
        }
    }
    return term;
}

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;
}