864 B | 864 chars
import sys
from math import sqrt, pi, sin, factorial
inp = lambda : sys.stdin.readline()[:-1].strip()
mii = lambda x = " " : [*map(int,inp().split(x))]
mfi = lambda x = " " : [*map(float,inp().split(x))]
ii = lambda : int(inp())
fi = lambda : float(inp())
p = print
def f(s, n):
ret = 0
for i in range(10):
k = 0
if s[i] == '?':
k = n
elif s[i] == 'X':
k = 10
else:
k = int(s[i])
ret += k * (10 - i)
return ret
def solve():
s = input()
idx = -1
sm = 0
for i in range(10):
if s[i] == '?':
idx = i
continue
k = 10
if idx == 9:
k = 11
for i in range(k):
k = f(s, i)
if k % 11 == 0:
if i == 10:
p("X")
else:
p(i)
return
p(-1)
if __name__ == "__main__":
tc = 1
for t in range(1, tc+1):
solve()