题目描述：
代码如下：
//7-15
#include <stdio.h>
#include <math.h>
double fact( int n );
int main ( void )
{
double e;
scanf( "%lf", &e );
int i = 1;
double temp = 1, fz, fm = 1, sum = 0, t = 1;
while( temp >= e ){
sum += temp;
fz = fact( i++ );
fm = fm * ( t + 2 );
temp = fz / fm;
t += 2;
}
sum += temp;
printf( "%lf", sum * 2 );
return 0;
}
double fact( int n )
{
double ret = 1;
for( int i = 1; i <= n; i++ )
ret *= i;
return ret;
}