C :

#include<stdio.h>
#include<math.h>
int main()
{
  float a,b,p,d,r,m;
  d=300000;
  p=6000;
  r=0.01;
  a=log(p/(p-d*r));
  b=log(1+r);
  m=a/b;
  printf("m=%.1f",m);
  return 0;
}
  

C++ :

#include<cstdio>
#include<cmath>
int main()
{
	double d=300000,p=6000,r=0.01,m;
	m=log10(p/(p-d*r))/log10(1+r);
	printf("m=%.1lf\n",m);
	return 0;
}