String Manipulation

Given a string : abbbccddddeee
Encode it to : ab3c2d4e3

#include<iostream>
#include <strstream>
#include<stdlib.h>
#include<string.h>
using namespace std;
void convert(char *input)
{
        char *start = input;
        char *s1 = input;
        char *s2 = input + 1;

        int len = strlen(input);
        int count = 0;
        char *end = start;
        while(--len && *s1 && *s2 )
        {
                while(*s1 && *s2 && len && *s1 == *s2)
                {
                        ++count;
                        s2++;
                        --len;
                }
                if(count)
                {
                        ostrstream str;
                        str<<(count+1);
                        *start = *s1;
                        *++start = *(str.str());
                        start = start + strlen(str.str()) - 1;
                        count = 0;
                }
                else
                        *start = *s1;
                start++;
                s1 = s2;
                s2++;
        }
        if(*s1 != *(s1-1))
                *start++ = *s1;
        *start = *s2;
        cout<<"Magic: "<<end<<endl;
        return;
}
int main()
{
        char input[100];
        memset(input, 0, 100);
        cout<<"Enter the string: ";
        scanf("%s", input);
        cout<<"You entered: "<<input<<"!!\n";
        convert(input);
        return 0;
}