#include<iostream> using namespace std; int main() { int n,x,y; cin>>n>>x>>y; if(n*y<=x) { cout<<"0"; } if(x%2==1&&x<n*y&&x>0) { cout<<y-x/n-1; } if(x%2==0&&x<n*y&&x>0) { cout<<y-x/n; } return 0; }