/*
TASK:minjumps
LANG:C++
*/
#include<iostream.h>
#include<math.h>
int main()
{long a,b,n,i,j,min=10000;
long long m;
cin>>a>>b>>n;
for(i=-abs(n);i<=abs(n);i++)
for(j=-abs(n);j<=abs(n);j++)if(a*i+b*j==n){m=abs(i)+abs(j);if(min>m)min=m;} 
if(min==10000){cout<<-1<<endl;return 0;}
cout<<min<<endl;
return 0;
}