a=list(input())
b=-1
Cnt=0
for i in a:
if(i=='*'): b=Cnt
Cnt+=1
S=0
Cnt=0
for i in a:
if(i!='*'):
if(Cnt%2==0):
S+=int(i)
else:
S+=int(i)*3
Cnt+=1
for i in range(0,10):
if(b%2==0):
if((S+i)%10==0):
print(i)
break
else:
if((S+i*3)%10==0):
print(i)
break