#include <stdio.h>
int hoge(int n){     int i, x0 = 0, x1 = 1, x;

    if(n == 0) return 0;
    if(n == 1) return 1;

    for(i = 2; i <= n; i++){
        x = 4 * x1 + 3 * x0;
        x0 = x1;
        x1 = x;
    }

    return x1;


}
int main(){
printf("%d",hoge(3));
return 0;
}