View Code of Problem 3834

#include<stdio.h>
int main(void){
	int n;
	while(scanf("%d",&n)!=EOF){
		long long count[n];
		count[0]=2;
		count[1]=5;
		for(int i=2;i<n;i++){
			count[i]=count[i-1]*3-1;
		}
		printf("%lld\n",count[n-1]);
	}
}