USACO1.3.2 Barn Repair (barn1)

/*
ID:shijiey1
PROG:barn1
LANG:C++
*/
#include <cstdio>
#include <cstring>
#include <algorithm>

using namespace std;

int m, s, c;
int arr[210];
int spacing[210];

bool cmp(int a, int b) {
return a > b;
}

int main() {
freopen("barn1.in", "r", stdin);
freopen("barn1.out", "w", stdout);
scanf("%d %d %d", &m, &s, &c);
for (int i = 0; i < c; i++) {
scanf("%d", &arr[i]);
}
sort(arr, arr + c);
for (int i = 1; i < c; i++) {
spacing[i - 1] = arr[i] - arr[i - 1];
}
int len = arr[c - 1] - arr[0] + 1;
sort(spacing, spacing + c - 1, cmp);
int blank = 0;
for (int i = 0; i < m - 1; i++) {
blank += spacing[i];
}
blank -= m - 1;
if (c <= m) {
printf("%d\n", c);
} else printf("%d\n", len - blank);

return 0;
}