C++ :

#include <iostream>
using namespace std;
int main()
{
	int n,m,p;
	cin>>n>>m>>p;
	int i;
	int count=0;
//	double x1,x2, x; 
	int x1,x2, x; 
	for(i=1;i<m;i++)
	{
	//	x1=(double)n*i/m;
	//	x2=p+(double)(n-p)*i/m;
	//	x=x2-x1; 
	x1=n*i/m;x2=p+(n-p)*i/m;	x=x2-x1; 
		count+=x;
		if((int)x2==p+(n-p)*i/m)   count--;
		//cout<<x1<<" "<<x2<<" "<<x<<" "<<count<<endl; 
		
	}
	
   cout<<count<<endl;	
	
	return 0;
}