#include<stdio.h> #include<math.h> int isrish(int a){ int i; if(a==1 || a==0) return 1; for(i=2;i<=sqrt(a);i++){ if(a%i==0){ return 1; } } return 0; } int main() { int i,a,b,sum,x[1000001]; sum=0; for(i=0;i<1000001;i++){ if(isrish(i)==0) sum++; x[i] = sum; } while(scanf("%d%d",&a,&b)!=EOF) { if(x[a]>x[a-1]){ printf("%d\n",x[b]-x[a]+1); } else printf("%d\n",x[b]-x[a]); } return 0; } |
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