#include<stdio.h>
#include<math.h>

void run(void){
  long long int n;
  scanf("%lld",&n);
  if(n<=3){
    printf("1\n");
  } else {
    printf("%d\n",(int)sqrt(n/3));
  }
  return;
}

int main(void){
  run();
  return 0;
}