#include <bits/stdc++.h>
using namespace std;
int dp[1000];
int bio(int n, int r) {
if(n == 1 ||n == 0 || (n == r)||(n == n && r == 0))
return 1;
else if(dp[n] == 0) {
return bio(n - 1, r -1) + bio(n -1 ,r);
}
}
int main()
{
int x, n, r;
scanf("%i %i", &n, &r);
x = bio(n, r);
printf("%i\n", x);
return 0;
}
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