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Cod sursa(job #173815)
#include <stdio.h>
FILE *f=fopen("fractii.in","r");
FILE *g=fopen("fractii.out","w");
unsigned long n, a[2][1000000],i ,j;
long long s;
int prim (unsigned long a, unsigned long b)
{if (a==1||b==1)
return 1;
else
if (a==b)
return 0;
else
{unsigned long r=a%b;
while (r!=0)
{a=b;
b=r;
r=a%b;
}
if (b==1)
return 1;
}
return 0;
}
void main()
{fscanf(f,"%l",&n);
for (i=1; i<n; i++)
{for (j=i; j<=n; j++)
if (prim(i,j))
a[1][j]=a[1][j-1]+1;
else
a[1][j]=a[1][j-1];
for (j=1; j<=n; j++)
{a[0][j]=a[0][j]+a[1][j];
a[1][j]=0;
}
}
s=n*n-(a[0][n]-a[0][n-1]);
fprintf(g,"%l\n",s);
fcloseall();
}