The calculation of GPA

 1 #include <stdio.h>
 2 
 3 int main(){
 4     int n;
 5     double s;
 6     double p;
 7     double totalS;
 8     double totalP;
 9     
10     while(scanf("%d",&n)!=EOF){
11         totalS=0;
12         totalP=0;
13         
14         while(n--){
15             scanf("%lf%lf",&s,&p);
16             
17             if(p==-1)
18                 continue;
19             
20             totalS+=s;    
21             if(p>=90){
22                 totalP+=s*4;
23             }
24             
25             else if(p>=80){   //这里改成p>=80 && p<=89就不行了不知道为什么，好郁闷。。。 
26                 totalP+=s*3;
27             }
28             
29             else if(p>=70){
30                 totalP+=s*2;
31             }
32             
33             else if(p>=60){
34                 totalP+=s;
35             }    
36         }
37         
38         if(totalS==0)
39             printf("-1\n");
40             
41         else
42             printf("%.2lf\n",totalP/totalS);    
43     }
44     return 0;
45 }