program c++ 'perhitungan nilai mahasiswa'

#include <iostream>
using namespace std;
int main()
{ float t1,t2,t3,t4,uts,uas,pres,nilai;
cout<<"berapa tugas 1= "<<endl;
cin>>t1;
cout<<"berapa tugas 2= "<<endl;
cin>>t2;
cout<<"berapa tugas 3= "<<endl;
cin>>t3;
cout<<"berapa tugas 4= "<<endl;
cin>>t4;
cout<<"berapa nilai uts= "<<endl;
cin>>uts;
cout<<"berapa nilai uas= "<<endl;
cin>>uas;
cout<<"berapa presensi= "<<endl;
cin>>pres<<endl;


nilai=((0.1*t1)+(0.15*t2)+(0.1*t3)+(0.15*t4)+(0.2*uas)+(0.2*uts)+(0.1*pres));
t1=0.1*t1;
t2=0.15*t2;
t3=0.1*t3;
t4=0.15*t4;
uts=0.2*uts;
uas=0.2*uas;
pres=0.1*pres;
cout<<"tugas 1  = "<<t1<<endl;
cout<<"tugas 2  = "<<t2<<endl;
cout<<"tugas 3  = "<<t3<<endl;
cout<<"tugas 4  = "<<t4<<endl;
cout<<"   uts   = "<<uts<<endl;
cout<<"   uas   = "<<uas<<endl;
cout<<"presensi = "<<pres<<endl;

if((nilai>=80) && (nilai<=100))
cout<<"nilai anda A"<<endl;
else
if((nilai>=60) && (nilai<=79))
cout<<"nilai anda B"<<endl;
else
if((nilai>=40) && (nilai<=59))
cout<<"nilai anda C"<<endl;
else
if((nilai>=20) && (nilai<=39))
cout<<"nilai anda D"<<endl;
else
cout<<"nilai anda E :( ";

cout<<"nilai akhir= "<<nilai<<endl;
}