#include <cstdio>

long long gcd(long long a,long long b){ return b?gcd(b,a%b):a; }

int main(){
    long long a,b,k;
    scanf("%lld%lld%lld",&a,&b,&k);
    long long L = 1, R = 1e18+7;
    long long res = -1;
    long long g = a*b/gcd(a,b);
    while(L<=R){
        long long M = (L+R)/2;
        long long have = M/a+M/b-M/g;
        if(have>=k){
            res = M;
            R = M-1;
        }
        else L = M+1;
    }
    printf("%lld\n",res);
    return 0;
}