import sys
import math
L,R,M=map(int,input().split())
a,r=L//M,L%M
b,u=R//M,R%M
if b>=a+2:
    print(M)
    sys.exit()
if b==a+1:
    print(min(M,M-r+u+1))
    sys.exit()
print(u-r+1)