#include<stdio.h>

int main(){
    long long n,m,dem,count=0;
    scanf("%lld", &n);
    m=n;
    while(n>=2){
        dem=0;
        n=n-3;
        dem++;
        count++;
        n=n+dem;
        if(n==2){
        	n=n+1;
		}
    }
    count=count+m;
    printf("%lld", count);
}