# -*- coding:utf-8 -*-
if __name__ == '__main__':
    sn = tuple(input())
    cnt = {k: 0 for k in map(chr, range(ord('a'), ord('z') + 1))}
    for s in sn:
        cnt[s] += 1
    print(min(cnt['t'], cnt['r'], cnt['e'] // 2))