#include <stdio.h>
#include <stdlib.h>

int main() {
    int N, M;
    if (scanf("%d", &N) != 1 || N < 1) {
        printf("Invalid input\n");
        return 0;
    }
    if (scanf("%d", &M) != 1 || M < 1 || M > N) {
        printf("Invalid input\n");
        return 0;
    }

    int keys[1000];
    for (int i = 0; i < M; i++) {
        if (scanf("%d", &keys[i]) != 1 || keys[i] < 0) {
            printf("Invalid input\n");
            return 0;
        }
    }

    int table[100] = {0}; // 0: empty, 1: filled
    int totalProbes = 0;

    for (int k = 0; k < M; k++) {
        int key = keys[k];
        int pos = key % N;
        int offset = 1 + (key % (N - 1));
        int probes = 1;

        while (table[pos]) {
            pos = (pos + offset) % N;
            probes++;
        }

        table[pos] = 1; // insert key
        totalProbes += probes;
    }

    printf("%d\n", totalProbes);

    return 0;
}