题解 | 小红的矩阵

#include<bits/stdc++.h>
using namespace std;
#define int long long
int n,m,k;

int check(int mid){
	int sum=0;
	for(int i=1;i<=n;i++){
		sum+=min(m,mid/i);
		if(mid/i==0) break;
	}
	return sum;
}

void solve(){
	
	int l=1,r=n*m,mid,res;
	while(l<=r){
		mid=l+(r-l>>1);
		if(check(mid)>=k){
			r=mid-1;
			res=mid;
		}else{
			l=mid+1;
		}
	}
	cout<<res<<endl;
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(0);
	
	cin>>n>>m>>k;
	
	solve();

    return 0;
}