// https://omegaup.com/arena/problem/Practicando-ciclos
#include <iostream>

int main( ) {
   int n, a, b;
   std::cin >> n >> a >> b;

   int v = n;
   while (v < 1000) {
     if (v % 2 == 0) {
        for (int i = 1; i <= a; i += 1) {
           v += i;
        }
     } else {
        for (int i = 1; i <= b; i += 1) {
           v += i;
        }
     }
   }

   std::cout << v;
}