inp = input()

for name in list('tre'): exec(f"{name} = 0")

for c in inp:
    if c == 't':
        t += 1
    elif c == 'r':
        r += 1
    elif c == 'e':
        e += 1
    
tree = 0
while t > 0 and r > 0 and e > 1:
    t -= 1
    r -= 1
    e -= 2
    tree += 1

print(tree)