Cod sursa(job #823145)
Utilizator | Data | 24 noiembrie 2012 17:44:32 | |
---|---|---|---|
Problema | Fractii | Scor | 50 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.42 kb |
#include<stdio.h>
int c[1000001];
void ciur(){
int i,j;
for(i=1;i<=100001;i++){
c[i]=i;
}
for(i=2;i<=100001;i++){
if(c[i]==i){
for(j=i;j<=100001;j+=i){
c[j]=c[j]/i*(i-1);
}
}
}
}
int main(){
freopen("fractii.in","r",stdin);
freopen("fractii.out","w",stdout);
int n,i;
long long s=0;
ciur();
scanf("%d",&n);
for(i=2;i<=n;i++){
s+=c[i];
}
printf("%lld\n",s*2+1);
return 0;
}