#include <fstream>

using namespace std;

int main()
{
    ifstream fin ("pinochio.in");
    ofstream fout("pinochio.out");
    int n,k,p;
    fin>>n>>p>>k;
    if(k%7==0)
        fout<<n+k/7*5*p-2*k/7;
    else
    if(k%7==1)
        fout<<n+k/7*5*p+p-2*k/7;
    else
    if(k%7==2)
        fout<<n+k/7*5*p+p+p-2*k/7;
    else
    if(k%7==3)
        fout<<n+k/7*5*p+p+p+p-2*k/7;
    else
    if(k%7==4)
        fout<<n+k/7*5*p+p+p+p+p-2*k/7;
    else
    if(k%7==5)
        fout<<n+k/7*5*p+p+p+p+p+p-2*k/7;
    else
    if(k%7==6)
        fout<<n+k/7*5*p+p+p+p+p+p-2*k/7-1;
    fin.close();
    fout.close();
    return 0;
}