A, B, C = map(int, input().split())

# n = A + B - C
# print(n)
# if A + B <= C:
#     print("impossible")
n = A + B - C
    # elif n > 10^100:
    #     print("impossible")
if n <= 10 and A >= n:
    print("a")
elif n <= 10 and A <n:
    print(A+10*(n-A))
elif n > 10 :
    n1 = n + n//10
    if n1 <= A:
        n2 = n1 - n1//10*10
        print(n2)