d=list(map(int,input().split(",")))
key=int(input())
i = 0
j = len(d) - 1
while __________:
    m = (i+j) //2
    if d[m] == key:           
        break
    if __________:            
        j = m - 1
    else:                    
        i = m + 1
if __________:
    print(m)
else:
    print(-1)