C :

#include <math.h>
#include "stdio.h"
 
int Monkey(int n, int x){
    if (x == n) {
        return 1;
    }
    return (Monkey(n, x+1)+1)*2;
}
int main() {
    int n;
    scanf("%d", &n);
    printf("x=%d\n", Monkey(n, 1));
    return 0;
}