#include <bits/stdc++.h>

 using namespace std;

 long long n,m,k;

 int Slove(long long mid) {

     long long sum = ;

     if(k>=mid)

     {

         sum+=(+mid)*mid/;

         sum+=(k-mid);

     }

     if(k<mid) {

         sum+=((mid-k+)+mid)*k/;

     }

     if(k+(mid-)<=n) {

         sum+=(+mid)*mid/;

         sum+=n-(k+(mid-));

     }

     if(k+(mid-)>n) {

         sum+=(mid+(mid-n+k))*(n-k+)/;

     }

     if(sum-mid<=m) return ;

     else return ;

 }

 int main()

 {

     //scanf("%d%d%d",&n,&m,&k);

     cin>>n>>m>>k;

     long long ans = ;

     long long l = ;

     long long r = m;

     while(l<=r) {

         long long mid = (l+r)/;

         if(Slove(mid)==) {

             ans = mid;

             l = mid+;

         }

         else r = mid-;

     }

     cout<<ans<<endl;

     return ;

 }