import sys

n, b  = map(str,sys.stdin.readline().split())

dict = {'0':0,'1':1,'2':2,'3':3,'4':4,'5':5,'6':6,'7':7,'8':8,'9':9,
        'A':10,'B':11,'C':12,'D':13,'E':14,
        'F':15,'G':16,'H':17,'I':18,'J':19,
        'K':20,'L':21,'M':22,'N':23,'O':24,
        'P':25,'Q':26,'R':27,'S':28,'T':29,
        'U':30,'V':31,'W':32,'X':33,'Y':34,
        'Z':35}

sum = 0

for i in range(len(n)) :
    sum+= dict[n[i]]*pow(int(b),len(n)-i-1)

print(sum)
