#include<bits/stdc++.h>
using namespace std;
#define rep(i,n) for(int i=0; i<(n); ++i)
using ll = long long;

int main(){
    vector<ll> a(3);
    rep(i,3) cin >> a[i];
    ll x = a[1] - a[0];
    ll y = a[2] - a[1] - 1;

    cout << min(x,y) << endl;
}