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  1. #include <stdio.h>
  2. #define FIN "fractii.in"
  3. #define FOUT "fractii.out"
  4.  
  5. void computePHI(long long int n, long long int *ptr) {
  6.      long long phi[n+1];
  7.      long long sum = 0;
  8.      for(int i = 1; i <= n; ++i) phi[i] = i;
  9.      for(int i = 2; i <= n; ++i) {
  10.          //daca este numar prim
  11.          if(phi[i]==i) {
  12.             for(int j = i; j <= n; j+=i) {
  13.                 phi[j] = phi[j] / i * (i - 1);
  14.             }
  15.          }
  16.          sum+=phi[i];
  17.      }
  18.      *ptr=(sum<<1)+1;
  19. }
  20.  
  21. int main(int argc, char const *argv[]) {
  22.   long long n, ans;
  23.   //freopen(FIN, "r", stdin);
  24.   //freopen(FOUT, "w", stdout);
  25.   scanf("%lld",&n);
  26.   computePHI(n,&ans);
  27.   printf("%lld",ans);
  28.   return 0;
  29. }
  30.  
Success #stdin #stdout 0.01s 5292KB
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https://ideone.com/00ezCv
fractii infoarena
language:
C (gcc 8.3)
created:
100 days ago
visibility:
secret

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