#include <stdio.h>
#include <math.h>
long permutations(long n, long k){
        long result = 1;
        for (int i = 0; i < k; ++i){
                result *= n-i;
        }
        return result;
}
int main(){
        int n, k, x;
        scanf("%d %d %d", &n, &k, &x);
        long result = 0;
        long value;
        if(x == 0){
            while(1 == scanf("%ld",&value));
            result = value;
        }else if (x == 1){
            if (k == 0){
                while(1 == scanf("%ld", &value)){
                    result += value;
                }
            }else{
                int index = 0;
                while(1 == scanf("%ld",&value)){
                    result += value*permutations(n-index,k);
                    index++;
                }
            }
        }else if (x == -1){
            if(k == 0){
                short index = (n-k) % 2 ? -1 : 1;
                while(1 == scanf("%ld",&value)){
                    result += index*value;
                    index *= -1;
                }
            }else{
                short flag = (n-k) % 2 ? -1 : 1;
                int index = 0;
                while(1 == scanf("%ld",&value)){
                    result += flag*value*permutations(n-index,k);
                    flag *= -1;
                    index++;
                }
            }
        }else{
            int index = 0;
            while(index <= (n-k) && 1 == scanf("%ld",&value)){
                result += value*permutations(n-index,k);
                if(index != (n-k)){
                    result *= x;
                }
                index++;
            }
        }
        printf("%ld\n", result);
    return 0;
}