【UVa】[1524]Hot or Cold?

#include<stdio.h>
#include<math.h>
double a[120];
double f(int n,double m) {
double sum=0;
for(int i=0; i<=n; i++) {
sum+=(double)pow(m,(double)(i+1))*a[i]/(i+1);
}
return sum;
}
int main() {
int n;
while(scanf("%d",&n),n) {
for(int i=n; i>=0; i--)
scanf("%lf",&a[i]);
double s,e;
scanf("%lf %lf",&s,&e);
printf("%.3lf\n",(f(n,e)-f(n,s))/(e-s));
}
return 0;
}