#include <bits/stdc++.h>   using namespace std;   long long k, d, t;   int main() {     scanf( %lld%lld%lld , &k, &d, &t);     t *= 2;     long long round = ceil((double)k / d) * d;     long long num = k * 2 + (round - k);     long long cnt = t / num;     long long left = t - cnt * num;     double ans = 0.0;     if (left <= k * 2) {       ans = cnt * round + left / 2;       if (left % 2) ans += 0.5;     } else       ans = cnt * round + k + (left - k * 2);     printf( %.1lf n , ans);     return 0;   }   