Multiplying large numbers

#include<iostream>
#include<cstring>
#include<cstdio>
using namespace std;
int a[10005],b[10005],c[10005];
int main()
{
char a1[10005],b1[10005] ;
int lena,lenb,lenc,i,j,x;
cin>>a1>>b1;
lena=strlen(a1);
lenb=strlen(b1);
for(i=0;i<=lena-1;i++ ) a[lena-i]=a1[i]-48;
for(i=0;i<=lenb-1;i++) b[lenb-i]=b1[i]-48;
for(i=1; i<=lena;++i)
{
x=0;//Store carry
for(j=1;j<=lenb;++j)//Process each bit of the multiplier 
{
c[i+j -1]=a[i]*b[j]+x+c[i+j-1];//Current product + last product carry + original number
x=c[i+j-1]/10;
c[i+j-1]%=10; 
} 
c[i+lenb]=x;//carry 
}
lenc=lena+lenb;
while(c[lenc]==0&&lenc>1) lenc--;//删除前导0
for(i=lenc;i>=1;i--)
cout<<c[i];
cout<<endl; 
return 0;
}