#include <iostream>
#include <vector>
#include <map>
#include <algorithm>
using namespace std;

#define REP(i,s,e) for (i = s; i <= e; i++)
#define rep(i,n) REP (i,0,(int)(n)-1)
#define RREP(i,s,e) for (i = s; i >= e; i--)
#define rrep(i,n) RREP (i,(int)(n)-1,0)
#define INF (int)1e8
#define MOD (int)(1e9+7)

typedef long long ll;

int main(void) {
    int a, b, t;
    cin >> a >> b >> t;
    int ans = ((t - 1) / b + 1) * b;
    for (int i = 0; b * i <= t && i <= a; i++)
        ans = min(ans,b * i + ((t - b * i - 1) / a + 1) * a);
    cout << ans << endl;
    return 0;
}