/*
TASK: minjumps
LANG: C++
*/
#include<iostream>
using namespace std;
int main(){
    int a,b,n;
    cin>>a>>b>>n;
    int i, sum1=0;
    if(a%2==0&&b%2==0&&n%2!=0){ cout<<-1<<endl;  return 0;}
    else if(a>=b && a%2==0 && n%2==0 && a<n && n%a==0){cout<<n/a<<endl;  return 0;}
    else if(b>a && b%2==0 && n%2==0 && b<n && n%b==0){ cout<<n/b<<endl;  return 0;}
    else{
        int sum=0;
        int br=0;
         while(sum<=n){
                sum+=a;
                if(sum==n) break;
                br++;
            }
         if(sum==n){ cout<<br<<endl;  return 0;}
         else if(sum>n){   
                sum1=sum; 
           while(sum1>=0){
                
            sum1=sum1-a;
            br--;
            sum=sum1;
             while(sum<=n){
                    sum+=b;
                     if(sum==n) break;
                    br++;
                }
            if(sum==n){ cout<<br<<endl;   return 0;}
            else sum=sum1;
            }
            
            
            sum=0;
            br=0;
             while(sum<=n){
                sum+=b;
                if(sum==n) break;
                br++;
            }
            sum1=sum;
             while(sum1>=0){
                
            sum1-=b;
            br--;
            sum=sum1;
             while(sum<=n){
                    sum+=a;
                     if(sum==n) break;
                    br++;
                }
            if(sum==n){ cout<<br<<endl;   return 0;}
            else sum=sum1;
            }
            
            
            
            
            if(sum>n){
                sum=0;
                br=0;
                int p=0;
                int sum1=0;
                for(i=0;i<10000/a;i++){
                    sum1-=a; br++;
                    sum=sum1;
                    while(sum!=n){
                        sum+=b;
                         if(sum==n) break;
                        p++;
                    }
                    if(sum==n){cout<<br+p<<endl;  return 0;}
                    else sum=sum1;
                }
                br=0;
                sum=0;sum1=0;
                for(i=0;i<10000/b;i++){
                    sum1-=b;
                    br++;
                    p=0;
                    sum=sum1;
                    while(sum<=n){
                        sum+=b;
                        if(sum==n) break;
                        p++;
                    }
                    if(sum==n){cout<<br+p<<endl;  return 0;}
                    else sum=sum1;
                }
            }
        }          
                        
}
cout<<-1<<endl;
system("pause");
return 0;
}        
                
                
            
