C :

#include<stdio.h>
#include<string.h>
double dp[57][57];
int main()
{
	int t;
	while(scanf("%d",&t),t)
	{
		int i,j;
		double a,b,c,d,e;
		scanf("%lf%lf%lf%lf%lf",&a,&b,&c,&d,&e);
		memset(dp,0,sizeof(dp));
		dp[t][1]=0;
		for(i=1;i<=t-1;i++)	
		{
			dp[t][i+1]+=(dp[t][i]+1);
		}
		for(i=t-1;i>=1;i--)
		{
			dp[i][1]+=a*(dp[i+1][1]+1)+b*(dp[i+1][2]+1);
			for(j=2;j<=i;j++)
			dp[i][j]+=c*(dp[i+1][j]+1)+d*(dp[i+1][j+1]+1)+e*(dp[i][j-1]+1);
		}
		printf("%.2lf\n",dp[1][1]);
	}
	return 0;
}

C++ :

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <string>
#include <iostream>
#include <map>
#include <vector>
#include <algorithm>
using namespace std;
#define MAXN 1000
#define eps 1e-8
double Atex[MAXN][MAXN];
double a[2], b[3];
int all;
inline int dcmp(double d) {
    return d < -eps ? -1 : d > eps;
}

void gauss(int n, int m)
{
    int r,c,i,j;
    for(r=c=0; r<n&&c<m; r++,c++)
    {
        for(i=r;i<n;i++)
        if(dcmp(Atex[i][c])) break;
        if(i==n)//{r--;continue;}
            return;
        if(i!=r) for(j=c;j<=m;j++) swap(Atex[i][j],Atex[r][j]);
        for(i=r+1;i<n;i++)
            if(Atex[i][c]!=0)
            {
                double temp=Atex[i][c]/Atex[r][c];
                for(j=c;j<=m;j++)
                Atex[i][j]-=Atex[r][j]*temp;
            }
    }
    for(i=n-1;i>=0;i--)
    {
        Atex[i][m]/=Atex[i][i];
        Atex[i][i]=1;
        for(j=i-1;j>=0;j--) Atex[j][m]-=Atex[i][m]*Atex[j][i];
    }
    return;
}

void makemap(int n) {
    memset(Atex, 0, sizeof(Atex));
    all = (1+n)*n/2;
    for (int i = 0; i < all; i ++) {
        Atex[i][i] = 1;
        Atex[i][all] = 1;
    }
    int t = 0, tt;
    for (int i = 0; i < n-1; i ++) {
        tt = t + i+1;
        Atex[t][tt] = -1*a[0];
        Atex[t][tt+1] = -1*a[1];
        for (int j = t+1; j < tt; j ++) {
            Atex[j][j+i+1] = -1*b[0];
            Atex[j][j+i+2] = -1*b[1];
            Atex[j][j-1] = -1*b[2];
        }
        t = tt;
    }
    Atex[t][all] = 0;
    for (int i = t+1; i < all; i ++) {
        Atex[i][i-1] = -1;
    }
}

int main()
{
    int n;
    while(scanf("%d", &n) != EOF) {
        if(n == 0) break;
        for (int i = 0; i < 2; i ++) {
            scanf("%lf", &a[i]);
        }
        for (int i = 0; i < 3; i ++) {
            scanf("%lf", &b[i]);
        }
        makemap(n);
        gauss(all, all);
        printf("%.2f\n", Atex[0][all]);
    }
    return 0;
}