How can I find a string in sequence (with Booleans)?

[go127a]

I have wrote it in this way. but some one told me that I can Use Boolean-without any further info and I am wonder how?!!

firststring = input() #ahhellllloou
to_find = "hello"

def check_string(firststring, to_find):
    c = 0
    for i in firststring:
        #print(i)
        if i == to_find[c]:
            c += 1
        if c == len(to_find):
        
            return "YES"
    return "NO"

print(check_string(firststring, to_find))