input: sortiran niz s dimenzije n, double x
output: 0<=i,j<=n-1, tako da s[i]+s[j]=x
i=0; j=n-1;
while (i<j)
{ if (s[i]+s[j]==x) {printf("%d %d", i, j); exit(0);}
  if (s[i]+s[j]<x) i++;
     else j--;   }