#include<bits/stdc++.h>
using namespace std;
int ans,money,a,b;
int main(){
    cin>>a>>b>>money;
    int i=1;
    while(a-i>=0&&b-i>=0){
        ans++;i++;
        a-=i;b-=i;
    }
    while(2*i-a-b < money){
        money=money-2*i+a+b;
        a=0,b=0;
        i++;ans++;
    }
    cout<<ans<<endl;
}