C++ :

#include<algorithm>
#include<bitset>
#include<cassert>
#include<cctype>
#include<cfloat>
#include<climits>
#include<cmath>
#include<cstdio>

using namespace std;

int main()
{
  long long n,m,k;
  while(scanf("%lld%lld%lld",&n,&m,&k)!=EOF)
  {
    long long l=0,r=n*m;
    bool tag=0;
    while(!tag)
    {
      long long res=0;
      long long mid=(l+r)>>1;
      long long now=m;
      long long res1=0;
      for(long long i=1;i<=n;i++)
      {
        for(;now>=1;now--)
        {
          if(i*now<mid)
          {
            res+=now;
            break;
          }
          else if(i*now==mid)
          {
            res1++;
            res+=now-1;
            break;
          }
        }
      }
      if(k>res&&k<=res+res1)
      {
        printf("%lld\n",mid);
        tag=1;
      }
      else if(k<=res)
        r=mid;
      else l=mid+1;
    }
  }
  return 0;
}