#include <cstdio>

int main() {
    int n, m, k, s;
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
    scanf("%d %d %d", &n, &m, &k );
    if (k < m + 1 )
        s = ((m / k) + (k - 1)) * n;
    else
        s = m * n;
    printf("%d", s);
    return 0;
}