#include<stdio.h> #include<string.h> int main(){ int q; scanf("%d",&q); while(q--){ long long m,n,i,j,k; scanf("%lld %lld",&n,&m); int a[10]; a[0] = m%10; long long int num = m*2; for(i = 1;i < 10; i++){ a[i] = a[i-1] + num%10; num = num+m; } // for(i = 0;i < 10; i++){ // printf(" %d ",a[i]); // } i = n/m; //共有多少个页数可加 k = i/10; //共有多少个a[10 ] j = i%10; //a[10]外有多少剩余 if(j!=0) printf("%lld\n",k*a[9]+a[j-1]); else printf("%lld\n",k*a[9]); } return 0; } |
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