View Code of Problem 73

#include <iostream>
#include <cstdio>
using namespace std;
int main(){
    int n,a[999],i;
    cin>>n;
    for(i=1;i<n;i++){
        a[1]=1;
        a[i+1]=(a[i]+1)*2;
    }
    if(i==n)
        cout<<a[i]<<endl;
    return 0;
}