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