from sys import stdin
##  input functions for me
def ria(sep = ''):
    if sep == '' :
        return list(map(int, input().split())) 
    else: return list(map(int, input().split(sep)))
def rsa(sep = ''):
    if sep == '' :
        return input().split() 
    else: return input().split(sep)
def ri(): return int(input())
def rd(): return float(input())
def rs(): return input()
##

## main ##
L, R, M = map(int, input().split())
if(L == R):
    print(1)
else:
    print((R - L + 1) % M if (R - L + 1) < M else M)