其实一句話總结就是：如果有非整数出现，一定是.5（可以分奇偶性证明之）
#include <iostream>
#include <stdio.h>
using namespace std;

int n;
double dist[33][33];
const double THRES = 1000000.0;

int main() {
	while(1){
		scanf("%d", &n);
		if(!n) return 0;
		for(int i = 1; i <= n; i++){
			dist[i][i] = 0;
			for(int j = i+1; j <= n; j++){
				int temp;
				scanf("%d", &temp);
				dist[i][j] = (double) temp;
				dist[j][i] = dist[i][j];
			}
		}
		double size = 0;
		bool valid[40];
		for(int i = 1; i <= n; i++) valid[i] = 1;
		for(int i = 1; i <= n-1; i++){

			for(int a = 1; a <= n; a++){
				if(!valid[a]) continue;
				for(int b = 1; b <= n; b++){
					if(!valid[b] || b==a) continue;
					double Dist = THRES;
					bool ky = 1;
					for(int c = 1; c <= n; c++){
						if(!valid[c] || c==a || c==b) continue;
						double tempDist = dist[a][c] - dist[b][c];
						if(Dist != THRES && tempDist != Dist){
							ky = 0;
							break;
						}
						Dist = tempDist;
					}
					if(ky){
						valid[b] = 0;
						size += dist[a][b];
						if(Dist != THRES){
							double dt = (Dist + dist[a][b])/2;
							for(int q = 1; q <= n; q++){
								if(!valid[q] || q==a) continue;
								dist[q][a] -= dt;
								dist[a][q] -= dt;
							}
						}
						goto onePhase;
					}
				}
			}
			onePhase:
			continue;
		}
		int size_ = (int)size;
		if(size-size_<0.4) printf("%d\n", size_);
		else printf("%d.5\n", size_);
	}
	return 0;
}