import os
import sys
from io import BytesIO, IOBase


def main():
    x,k,d = map(int,input().split())
    
    t = abs(x)//d
    
    if t<=k and x<0:
        x+=t*d
        k-=t
    elif t<=k and x>0:
        x-=t*d
        k-=t
    elif t>k and x<0:
        x+=k*d
        k-=k
    elif t>k and x>0:
        x-=k*d
        k-=k
    
    while k:
        if x<0:
            if x+d<0:
                x+=d
            elif abs(x+d)<=abs(x) and (k-1)%2 == 0:
                print(abs(x+d))
                break
            elif abs(x+d)<=abs(x) and (k-1)%2 != 0:
                print(abs(x))
                break
            elif abs(x+d)>=abs(x) and (k)%2 == 0:
                print(abs(x))
                break
            elif abs(x+d)>=abs(x) and (k)%2 != 0:
                print(abs(x+d))
                break
        else:
            if x-d>0:
                x-=d
            elif abs(x-d)<=abs(x) and (k-1)%2 == 0:
                print(abs(x-d))
                break
            elif abs(x-d)<=abs(x) and (k-1)%2 != 0:
                print(abs(x))
                break
            elif abs(x-d)>=abs(x) and (k)%2 == 0:
                print(abs(x))
                break
            elif abs(x-d)>=abs(x) and (k)%2 != 0:
                print(abs(x-d))
                break
        k-=1
    else:
        print(abs(x))
            
        
    

# region fastio
##
##BUFSIZE = 8192
##
##
##class FastIO(IOBase):
##    newlines = 0
##
##    def __init__(self, file):
##        self._fd = file.fileno()
##        self.buffer = BytesIO()
##        self.writable = "x" in file.mode or "r" not in file.mode
##        self.write = self.buffer.write if self.writable else None
##
##    def read(self):
##        while True:
##            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
##            if not b:
##                break
##            ptr = self.buffer.tell()
##            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
##        self.newlines = 0
##        return self.buffer.read()
##
##    def readline(self):
##        while self.newlines == 0:
##            b = os.read(self._fd, max(os.fstat(self._fd).st_size, BUFSIZE))
##            self.newlines = b.count(b"\n") + (not b)
##            ptr = self.buffer.tell()
##            self.buffer.seek(0, 2), self.buffer.write(b), self.buffer.seek(ptr)
##        self.newlines -= 1
##        return self.buffer.readline()
##
##    def flush(self):
##        if self.writable:
##            os.write(self._fd, self.buffer.getvalue())
##            self.buffer.truncate(0), self.buffer.seek(0)
##
##
##class IOWrapper(IOBase):
##    def __init__(self, file):
##        self.buffer = FastIO(file)
##        self.flush = self.buffer.flush
##        self.writable = self.buffer.writable
##        self.write = lambda s: self.buffer.write(s.encode("ascii"))
##        self.read = lambda: self.buffer.read().decode("ascii")
##        self.readline = lambda: self.buffer.readline().decode("ascii")
##
##
##sys.stdin, sys.stdout = IOWrapper(sys.stdin), IOWrapper(sys.stdout)
##input = lambda: sys.stdin.readline().rstrip("\r\n")

# endregion



import collections
if __name__=='__main__':
    main()
##    
##                    


Measured memory_bytes: 83764