TADM2E 8.13

             a=raw_input()                        # the input string
             m=raw_input().split(" ")             # the set of tokens separated by space
             n=len(m) 
             k=int(raw_input())                   # the maximum length of the token
             l=[9999999999]*(len(a)+1)     
             l[0]=0
             for i in range(1,len(a)+1):
              while(lm<i):
                 cost = 99999
                 if a[lm:i] in m:
                     cost=l[lm]+1
                 if cost < l[i] :
                     l[i] = cost
                 lm=lm+1
            print l[-1]

Python Based implementation