T105910 【模板】O(1)快速乘

#include<cstdio>
#include<iostream>
#define ll long long
#define ld long double
#define ul unsigned long long
using namespace std;
ll mul(ll a,ll b,ll p){
	ul first=(ul)a*b;
	ul second=((ll)((ld)a*b/p))*p;
	return (ll)(first-second);
}
int main(){
	ll a,b,p;
	cin>>a>>b>>p;
	ll ans=mul(a,b,p);
	cout<<ans<<endl;
	return 0;
}