#include <bits/stdc++.h>

using namespace std;

long long n,m,k,mm;

long long sum (long long n) {
    return n*(n+1)/2;
}

long long howmany(int p){
    long long left = k-1;
    long long right = n-k;

    long long res = p;
    if(left >= p-1) res += sum(p-1);
    else res += sum(p-1) - sum(p-1-left);

    if(right >= p-1) res += sum(p-1);
    else res += sum(p-1) - sum(p-1-right);

    return res;
}

long long Can(long long p){
    long long rr = howmany(p);

    if(rr <= mm) return 1;
    else return 0;
}

long long bins(){
    long long m,val,l,r;

    l = 0; r = mm;
    while(l<r){
        m = (l+r+1)/2;
        if(Can(m)) l = m;
        else r = m-1;
    }
    if(Can(l)) return l;
    else return -1;
}


int main() {
    cin >> n >> mm >> k;
    mm-=n;


    long long res = bins();
    cout<<res+1<<endl;

    return 0;
}