#include <ctype.h>
#include <stdio.h>

int main() {
    int l,r,x,y,result;
    scanf("%d %d %d",&l,&r,&x);
    for (int i = l;i <= r;i ++){
        if (i % x== 0){y = i;printf("%d",y);return 0;}
        else {result += 1;}
    }
    printf ("-1");
    return 0;
}