#include <bits/stdc++.h>
using namespace std;

long long a, b, x;
int main() {
    freopen("demso.inp" , "r" , stdin);
    freopen("demso.out" , "w" , stdout);
    ios_base::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);

    cin >> a >> b >> x;
    long long c = b / x - (a - 1) / x ; // dem so tu a den b chia het cho x 
    long long d = b - a + 1; // so so hang tu a den b 
    cout << d - c;
    return 0;
}

#include <bits/stdc++.h>
using namespace std;
#define int long long
signed main(){
	freopen("demso.inp","r",stdin);
	freopen("demso.out","w",stdout);
	int a,b,c;
	cin>>a>>b>>c;
	--a;
	cout<<b-a-((b/c)-(a/c));
}