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  1. #include <stdio.h>
  2.  
  3. int main(void){
  4.     int num,prime=2,euler;
  5.     scanf("%d",&num);
  6.     if(num<=0)
  7. 	return 0;
  8.     euler=num;
  9.     for(;prime*prime<=num;prime+=2){
  10.         if(num%prime==0){
  11.             euler=euler/prime*(prime-1);
  12.             while(num%prime==0)num/=prime;
  13.         }
  14.         if(prime==2)prime--;
  15.     }
  16.  
  17.     if(num>1){
  18.         euler=euler/num*(num-1);
  19.     }
  20.  
  21.     printf("φ(%d)=%d\n",num,euler);
  22.     return 0;
  23. }
Success #stdin #stdout 0.01s 5292KB
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φ(5)=8
https://ideone.com/UEdfcG
language:
C (gcc 8.3)
created:
4 days ago
visibility:
public

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