#include<stdio.h>
#include<string.h>

int main(void){
  int i, n = 0;
  char S[1000001], s[4];
  s[4] = '\0';
  scanf("%s", S);
  for(i = 0; S[i+3] != '\0'; i++){
    s[0] = S[i];
    s[1] = S[i+1];
    s[2] = S[i+2];
    s[3] = S[i+3];
    if(strcmp(s, "tree") == 0) n++;
  }
  printf("%d\n", n);
  return 0;
}