/*
TASK:minjumps
LANG:C++
*/
#include<iostream>
using namespace std;
int main()
{
 int a,b,c,m,br=1,br2=0;
 cin>>a>>b>>c;
 int k=b,p=a;
 if(c%a==0&&br==1){cout<<c/a<<"\n";br2++;br++; }
 if(c%b==0&&br==1){cout<<c/b<<"\n";br2++;br++; }
 if(b>a&&br==1)
 {
  while(b-a<c+1&&c%b!=0)
  {
   if(b-a==c){cout<<br+1<<"\n";br2++;}
   b=b+k; br++;
  }
 }
 if(a>b&&br==1)
 {
  while(a-b<c+1&&c%a!=0)
  {
   if(a-b==c){cout<<br+1<<"\n";br2++;}
   a=a+p; br++;
  }
 }
 int r;
 r=(p*c)-(k*c);
 if(br2==0)
 {
 if(r==c||r==-c)
 {cout<<c<<"\n";}
 else cout<<"-1\n";
 }
 return 0;
}
