#include <stdio.h>

int main(void) {

    int car_num, min, i, arr[100], sum = 0;

    scanf("%d %d", &car_num, &min);

    for(i = 0; i < min; i++)
    {
        scanf("%d", &arr[i]);
        if(sum + arr[i] - car_num < 0)
            sum += 0;
        else
        sum = sum + arr[i] - car_num;
    }

    printf("%d", sum);

    return 0;


}

You're not printing a newline after printing the answer ... though I think the real issue is different: I don't believe you're handling the following cases correctly.

Try this test case
5 3
6 1 2

and this one
5 3
6 1 7

Good luck!
-- DC

Edited by author 30.01.2015 21:10