#include <stdio.h>

// Recursive function to calculate the nth term
int find_nth_term(int n, int a, int b, int c) {
    // Base case: if n is 1, return a
    if (n == 1) {
        return a;
    }
    // Base case: if n is 2, return b
    else if (n == 2) {
        return b;
    }
    // Base case: if n is 3, return c
    else if (n == 3) {
        return c;
    }
    // Recursive case: calculate the nth term as the sum of the previous three terms
    else {
        return find_nth_term(n - 1, b, c, a + b + c);
    }
}

int main() {
    int n, a, b, c;

    // Read the input values
    scanf("%d", &n);
    scanf("%d %d %d", &a, &b, &c);

    // Calculate and print the nth term
    int result = find_nth_term(n, a, b, c);
    printf("%d", result);

    return 0;
}