Cod sursa(job #865373)
Utilizator | Data | 26 ianuarie 2013 13:47:33 | |
---|---|---|---|
Problema | Fractii | Scor | 90 |
Compilator | cpp | Status | done |
Runda | Arhiva de probleme | Marime | 0.43 kb |
#include<cstdio>
using namespace std;
const int LIM=1000010; int n;
long long v[LIM], sol=0;
int main(){
FILE *in=fopen("fractii.in","r"), *out=fopen("fractii.out","w");
int n;
fscanf(in, "%d\n", &n);
for(int i=2; i<=n; i++)
v[i]=i-1;
for(int i=2; i<=n; i++){
for(int j=2*i; j<=n; j+=i)
v[j]-=v[i];
sol+=2*v[i];
}
fprintf(out, "%lld\n", sol+1);
return 0;
}