Probability dp;
F[i] = (F[i] + 1) * p[i][0] + (F[i+1] + 1) * p[i][1] + (F[i+2] + 1) * p[i][2] ;
The portal:http://acm.tju.edu.cn/toj/showp3977.html\
//F[i] = (F[i] + 1) * p[i][0] + (F[i+1] + 1) * p[i][1] + (F[i+2] + 1) * p[i][2];
#include <cstdio>
#include <cstring>
#include <cstdlib>
#include <cmath>
#include <iostream>
#include <algorithm>
using namespace std;
double p[105][3];
double F[105];
void Deal_with() {
int n;
while(~scanf("%d",&n)) {
memset(F,0,sizeof(F));
for(int i = 1 ; i < n ; i++) {
scanf("%lf %lf %lf",&p[i][0],&p[i][1],&p[i][2]);
}
F[n] = 0;
F[n - 1] = 1 / p[n-1][1];
for(int i = n - 2 ; i >= 1 ; i--) {
F[i] = ( (F[i+1] + 1) * p[i][1] + (F[i+2] + 1) * p[i][2] + p[i][0] )/(1 - p[i][0]);
}
printf("%.2lf\n",F[1]);
}
}
int main(void) {
freopen("a.in","r",stdin);
Deal_with();
return 0;
}