#include <iostream>
using namespace std;
int main() {
long long int a,b,x,k;
cin >> a >> b >> x;
if ( (a%x==0) or (b%x==0) or (a%x > b%x )) k= (b-a)/x +1;
else k= (b-a)/x;
cout << k;
return 0;
}
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