题解（改版）

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#include<bits/stdc++.h>
using namespace std;
char str[114514];
int m,n,s[114514],top;
int main(){
ios_base::sync_with_stdio(false);
int i,len,X=0,x;
scanf("%d",&m);
scanf("%s",str+1);
len=strlen(str+1);
int M=1;
for(i=len;i>0;i--){
if('0'<=str[i]&&str[i]<='9')
X+=(str[i]-'0')*M;
else
X+=(str[i]-'A'+10)M;
M=m;
}
scanf("%d",&n);
while(X){
s[++top]=X%n;
X/=n;
}
while(top){
x=s[top];
top--;
if(x<=9)
putchar(x+'0');
else
putchar(x-10+'A');
}
return 0;
}