#include<cstdio>
#include<cmath>


using ll=long long;

int main(void)
{
	int b1, b2, b3;

	while(scanf("%d%d%d", &b1, &b2, &b3)==3)
	{
	// an+1 = r an + d
		
		double r=(double)(b2-b3)/(b1-b2);
		double d=b2-r*b1;
		ll b4=round(r*b3+d);
		printf("%lld\n", b4);
	}

	return 0;
}