29648번: Разрезание заготовки ↗

"""
[29648: Разрезание заготовки](https://www.acmicpc.net/problem/29648)

Tier: Bronze 3 
Category: arithmetic, bruteforcing, geometry, math
"""

import sys
from math import sqrt, pi, sin, factorial, ceil, floor
from datetime import datetime, timedelta

SYS_INPUT = True
RECURSION_LIMIT = 10 ** 7
SET_RECURSION = False
BLANK = " "

if SET_RECURSION:
  sys.setrecursionlimit(RECURSION_LIMIT)

inp = lambda : sys.stdin.readline().rstrip() if SYS_INPUT else input()
mii = lambda : [*map(int,inp().split())]
mfi = lambda : [*map(float,inp().split())]
ii = lambda : int(inp())
fi = lambda : float(inp())
isplit = lambda : inp().split()
p = print

def gcd(a, b): return gcd(b, a % b) if b > 0 else a
def lcm(a, b): return a * b // gcd(a, b)

def solve():
  a, b, s = mii()

  A = 1
  B = -(a + b)
  C = (a * b - s)

  D = B * B - 4 * A * C

  if D < 0 or int(sqrt(D)) ** 2 != D: 
    p(-1)
  else:
    p((-B + int(sqrt(D))) // 2)

if __name__ == "__main__":
  tc = 1
  for t in range(1, tc+1):
    ret = solve()