S=list(input ())
T=0
R=0
E=0
for i in range(len(S)):
    if S[i]=="t":
        T+=1
    elif S[i]=="r":
        R+=1
    elif S[i]=="e":
        E+=1
    T*=2
    R*=2
    if T<R:
        M=T
    else:
        M=R
    if E<M:
        M=E
print (M//2)