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  1. #include<stdio.h>
  2. void
  3. matrix_mul(long long int fibo[2][2],long long int whatever[2][2],long long int temp[2][2])
  4. {
  5. 	int i,j,k;
  6. 	int sum=0;
  7.  for(k=0;k<2;k++)
  8. 	{
  9. 		for(i=0;i<2;i++)
  10. 		{
  11. 				sum=0;
  12. 				for(j=0;j<2;j++)
  13. 				{
  14. 					sum+=fibo[k][j]*whatever[j][i];
  15. 					}
  16. 				temp[k][i]=sum;
  17. 			}
  18. 		}
  19. 	}
  20. int
  21. main()
  22. {
  23. 	long long int fibo[2][2]={{1,1},
  24. 							  {1,0}};
  25.     long long int previous[2][2]={{1,1},
  26. 					   			 {1,0}};
  27. 	long long int  temp[2][2]={{0,0},
  28. 					           {0,0}};
  29. 	int n;
  30. 	int i,j;
  31. 	scanf("%d",&n);
  32. 	n=n-1;
  33. 	while(n)
  34. 	{
  35.  
  36. 		if(n%2==1)
  37. 		{
  38.             matrix_mul(fibo,previous,temp);
  39. 		            for(i=0;i<2;i++)
  40. 		            {
  41. 						for(j=0;j<2;j++)
  42. 						{
  43. 								previous[i][j]=temp[i][j];
  44. 							}
  45. 						}
  46. 			}
  47. 			matrix_mul(fibo,fibo,temp);
  48. 					for(i=0;i<2;i++)
  49. 		            {
  50. 						for(j=0;j<2;j++)
  51. 						{
  52. 								fibo[i][j]=temp[i][j];
  53. 							}
  54. 						}
  55.     	n=n/2;
  56. 			}
  57. 			printf("%lld",previous[0][0]);
  58.  
  59. 	return 0;
  60. 	}
  61.  
  62.  
  63.  
stdin
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5
compilation info 
prog.c: In function ‘main’:
prog.c:31: warning: ignoring return value of ‘scanf’, declared with attribute warn_unused_result
stdout
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8
https://ideone.com/WrOu6
language:
C (gcc 8.3)
created:
13 years ago
visibility:
public

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