C程序----求序列前N项和

#include <stdio.h>
#include <stdlib.h>

int main()
{
      int mol = 2,deno = 1,temp;
      int i,n;
      float sum ;
      scanf("%d",&n);
      sum = (float)mol / deno;
      for(i = 1; i<n ; i++)
      {
          temp = deno ;
          deno = mol ;
          mol = mol + temp;
          sum = sum + (float)mol / deno ;
      }
      printf("%.2f\n",sum);
    return 0;
}