题解在此，讲的蛮清楚的->

我就贴个代码

1 //minamoto 2 #include
     
       3 #include
      
        4 #include
       
         5 using namespace std; 6 #define getc() (p1==p2&&(p2=(p1=buf)+fread(buf,1,1<<21,stdin),p1==p2)?EOF:*p1++) 7 char buf[1<<21],*p1=buf,*p2=buf; 8 inline int read(){ 9     #define num ch-'0'10     char ch;bool flag=0;int res;11     while(!isdigit(ch=getc()))12     (ch=='-')&&(flag=true);13     for(res=num;isdigit(ch=getc());res=res*10+num);14     (flag)&&(res=-res);15     #undef num16     return res;17 }18 char sr[1<<21],z[20];int C=-1,Z;19 inline void Ot(){fwrite(sr,1,C+1,stdout),C=-1;}20 inline void print(int x){21     if(C>1<<20)Ot();if(x<0)sr[++C]=45,x=-x;22     while(z[++Z]=x%10+48,x/=10);23     while(sr[++C]=z[Z],--Z);sr[++C]='\n';24 }25 inline char getop(){26     char ch;27     while((ch=getc())!='A'&&ch!='C');28     return ch;29 }30 const int N=150005,M=2005;31 int ans[M][M],v[N],s,n,m;32 int main(){33 //    freopen("testdata.in","r",stdin);34     n=read(),m=read(),s=pow(n,0.3333);35     for(int i=1;i<=n;++i){36         v[i]=read();37         for(int j=1;j<=s;++j)38         ans[j][i%j]+=v[i];39     }40     while(m--){41         char op=getop();int x=read(),y=read();42         switch(op){43             case 'A':{44                 if(x<=s) print(ans[x][y%x]);45                 else{46                     int res=0;47                     for(int i=y;i<=n;i+=x) res+=v[i];48                     print(res);49                 }50                 break;51             }52             case 'C':{53                 for(int i=1;i<=s;++i) ans[i][x%i]+=y-v[x];54                 v[x]=y;55                 break;56             }57         }58     }59     Ot();60     return 0;61 }