#include<stdio.h>

#define MaxN 805

int v[MaxN], sum[MaxN][MaxN], N;

int main(){
	freopen("nrtri.in", "r", stdin);
	freopen("nrtri.out","w", stdout);

	int i, j, nr, k;
	scanf("%d", &N);
	for(i = 1; i <= N; i++)
		scanf("%d",&v[i]);
	for(i = 1; i <= N; i++)
		for(j = 1; j <= N; j++)
			if(i!=j)
				sum[i][j] = v[i] + v[j];
	/*for(i = 1; i <= N; i++){
		for(j = 1; j <= N; j++)
			printf("%d ", sum[i][j]);
		printf("\n");
	}*/
	nr = 0;
	for(i = 1; i < N - 1; i++)
		for(j = i + 1; j < N; j++)
			for(k = j + 1; k <= N; k++){
				//printf("%d %d %d \n", sum[i][j], sum[j][k], sum[k][i]);
				if(sum[i][j] >= v[k] && sum[j][k] >= v[i] && sum[k][i] >= v[j])
					nr++;
			}
	printf("%d\n", nr);
	fclose(stdin);
	fclose(stdout);
	return 0;
}