#include <stdio.h>
int main()
{
    float a,b;
    int c;
    if(scanf("%f \n%f",&a,&b,&c)!=3 || (c!=0 && c!=1))
    {
        printf("Invalid iput");
    }
    else if (c==0)
    {
        printf ("Insufficient Balance");
    }
    else
    {
        printf("%.2f",b-a);
    }
}