# import sys; input = sys.stdin.buffer.readline
# sys.setrecursionlimit(10**7)
from collections import defaultdict
con = 10 ** 9 + 7; INF = float("inf")

def getlist():
	return list(map(int, input().split()))

#処理内容
def main():
	S = input()
	D = defaultdict(int)
	for i in S:
		if i == "t":
			D["t"] += 1
		elif i == "r":
			D["r"] += 1
		elif i == "e":
			D["e"] += 1

	ans = min(D["t"], D["r"], int(D["e"] // 2))
	print(ans)

if __name__ == '__main__':
	main()